When I go to the download page from where I can see my purchases it shows all of the downloads, even the new versions and there's no additional paywall. Also, if you go to that page it shows your options to get access to what you paid for if you no longer have access for some reason (such as contacting itch support). I believe that this issue is not actually on the dev of the game but rather on itch.
Viewing post in AFGirlfriend for Quest Mixed Reality/Pico 4 comments
no its definitely on the dev, because ive contacted support numerous times about this issue and have always been told its up to the author to fix the issue, but i guess youll find out yourself when he updates the game and you lose access to your files like i have when he changes the price for the 8th time