This is really cool!
(ps. the mac build works if you were wondering)
I am playing on a Mac, and when I play another Unity game after playing Direct Ascent, it opens in the same aspect ratio as direct ascent. This can be solved by deleting a file in ~/Users/USER_NAME/Library/Preferences/Unity, but I would prefer not to have to delete that file every time I want to play Hollow Knight.
[EDIT]: After testing, I have determined that this bug only affects older versions of Unity