You realize that you've been watching everything from Laminoir's point of view (one of the jurists).

Thalassa

BEGIN MASON SYSTEM [...]

Phoenix:
...Well now.
Shall we begin?

Phoenix:
Touch the arrow to switch
between past and present.

Phoenix:
But let's begin seven years
ago... in the past.

Phoenix:
It is right after my last
trial came to an abrupt end.

Phoenix:
...Now that you know the game,
let's play.

What is the MASON System? Is it a 'virtual reality system'? The game never says so. For example, Kay's simulations (which were less elaborate) came straight out of some magical 'object' but there's no such 'justification' here.

Is it what was shown to the in-world jurists? If the game is examined more closely, it shows it was not. Nor are we 'role-playing Thalassa', except right at the end.

It's ambiguous, but there's a clear dichotomy between the sequences where Phoenix addresses the in-world jury, and the ones where he's seeming to addressing the player directly. Aka US.

For example the end jury sequence there is no Matrix-type background, but the parts at the beginning where Phoenix speaks to 'us' there is. And all this stuff about a 'game', over and over. This sequence would surely never be said to the in-world jury:

============================
Episode 4
Turnabout Succession
MASON System -40M01-
============================

...That trial seven years ago
was the beginning of it all.

This I know beyond a doubt.

The mysteries of the past work
their magic on the present.

But you'll soon be finding
all of this out for yourself.

Which of Magnifi Gramarye's
disciples pulled that trigger?

Where did the vanishing
defendant, Zak Gramarye, go?

What dark truth lurks behind
the forged diary page?

And what about the girl who
was left behind...?

...The past left us these four
"keys" to unlocking the truth.

But that's not all.

There are four "keys" in the
present, as well.

And when all the questions
have found their answers...

...the final trial will
begin.


[See,. you really think in the in-world jury would hold up trial date till they finished? As for US PLAYING well of course this is logical.]


But first, you must chase the
truth through then and now.

Think of it... as a game.

Phoenix:
I, Phoenix Wright, will be
your guide through this game.

Phoenix:
That terrible trial saw me
present forged evidence.

Phoenix:
...It ended, half-finished,
when the defendant vanished.

Phoenix:
What became of me after
that...?

Phoenix:
As your investigation proceeds
the answer will become clear.

Phoenix:
...Oh, and one more thing.

Phoenix:
There is something I must
tell you.

Phoenix:
As Apollo Justice has his
bracelet...

[Would the jury know this? I don't think so!]

Phoenix:
...so, too, do I have my
own "weapon" of sorts.

Phoenix:
...My Magatama.

Phoenix:
What does it do, you ask?

Phoenix:
That I would have you see
for yourself.

Phoenix:
...Well now.
Shall we begin?

Phoenix:
Touch the arrow to switch
between past and present.

Phoenix:
But let's begin seven years
ago... in the past.

Phoenix:
It is right after my last
trial came to an abrupt end.

Phoenix:
...Now that you know the game,
let's play.

And would the in-world jury really have played Phoenix's Flashback Trial too? And that happens AFTER the MASON screen boots up, so it's clearly part of 'the MASON'.

In the Flashback Trial it's like the game throws the irony in our face. We can't choose to NOT present the forged evidence. The two options lead to the same thing. If we don't present it we never progress. We know exactly what's going to happen. The limitations of the game's options affecting our possible input are emphasised. The game and its writing is in control not the players.

So I think it's breaking the 4th wall. Maybe this is Phoenix's magical supernatural mentor power analogous to Mia. Instead of the spiritual plane, we get him able to manipulate the 'game' logic in the same weird old game travel/narrative sequences of GS1-3+ etc. which it's no 'accident' the MASON is fairly identical to. Because, hey people, this IS a videogame! Of course this was never explicitly said either. And since we'll probably never get to ask Takumi about his intentions for MASON (if indeed he is the one who came up with it.)

But it matches up with Hobo!Phoenix's character. He's not just forging cards, he's exploiting everything at his disposal, even the game's 'investigation-engine' things, and we're the targets here, the ones playing the game, not the people in-world. The in-world jury was shown something else, not literally what we played. Whatever WE see though, is some kind of weird spin (artistic comment? certainly a deconstruction) on the investigation-engine underpinning the game.

The MASON boot screen loads before the start of 4-4 and its Flashback trial, way before we actually 'play the game'. In the intro video for 4-4, Vera collapses in it. The 'time sequence' is an utter mess, and this intro can't be taken literally.

The only part where the player is 'Thalassa' is right at the end. Right at the end Phoenix talks to the actual jurists "Choose wisely. Choose well." But in a lot of other times in 4-4 he's addressing the player. It's only his final speech before the verdict that's to the in-game jurists.

The final verdict has no Matrix-syle background behind Phoenix - it's just black, and UNLIKE the MASON intro, has a location:
October 9, 12:48 PM
Jurists' Chambers