I did not find that part. To the contrary.
https://itch.io/docs/legal/terms#4-publisher-content is quite clear. The publisher can remove the content. Is there maybe a faq that says otherwise? Because the faq I found directed to the tos.
They cannot revoke the license though. However that works out, if you do not have the files because you trusted that in the digital age you could download it from the cloud service where you paid for the game.
From a digital download store perspective it is quite bad to remove (paid) games. I would wish for better and clearer rules about that. Like freezing a version for existing customers and refusing new customers.