Man, everyone is intoning really weirdly in the trailer, I wonder if the voice acting is still an early draft?

It's definitely full of attempts to sync with lip flaps, even if that means pausing the speech at times that make it unnatural. It's hard to say if it's a rough draft, if they didn't get modified animation from the studio to better match English voice acting yet, or if this is intended to be final.

Considering this game is coming out a month from today worldwide (except 3DS), I would guess this is meant to be final unless the wrong trailer was released. Fixing this sort of thing would likely not be possible this late. Then again, there are some odd things about the trailer like "LAYTON series NEW EPISODE", so maybe it is the wrong, incomplete trailer?

Level-5 confuse me with their handling of it, blah. It feels like they made it and were like "OH SHIT WE FORGOT TO MAKE IT IN ENGLISH" like an afterthought

To help promote the upcoming Layton’s Mystery Journey: Katrielle and The Millionaires’ Conspiracy for 3DS, Level-5 teamed up with SCRAP (real escape games) to make a "puzzle-solving event that challenges users around the world to solve 50 puzzles that appear on the internet and in special locations in 10 countries, including Japan, the U.S., the U.K., South Korea, and Australia" from June 20 to September 21, 2017.

https://layton.world

From Destructoid

There's some puzzles to solve (the first one feature the Pen-Pineapple-Apple-Pen guy), others you need to wait until unlock.
I guess the trailer was a rushed release to promote the site that was already online.

I already did the 3/50 unlocked. The second one is some top tier Layton puzzle you'd only see at the end :V

Trailer was removed.