Still the 23rd! Not sure where they got that date from.
They likely got it from the game's IndieDB page. It was listed on there to release May 31 before we knew the actual release date. That's my doing, as the choice was to either set a precise release date, or select TBA. Since I knew we were planning to launch in May, I defaulted to the last day of the month. Anyway, it's been updated since, but apparently not before the piece was researched.