The mails from such a mailing list might come from the Itch mail server, but they are not sent by Itch. As is evident by the reply-to mail adress, which is the developer's.
Also, this is not a bundle issue. This automatic mailing list opt-in goes for all purchases.
The actual Itch mailing lists and other emails you would receive are configurable in your settings.
What would be ok, is a button and a suggestion to subscribe to a mailing list on the purchase page. Or at least an unsubscribe button there, instead of only showing it to users when they receive a mail.
But frankly, I believe this whole feature is outdated and deprecated by the follow mechanism and devlogs. The mailing list thingy might be of interest for people that do not have an account and cannot follow. But you can not configure it on the purchase page. Also it is just not common for developers to mail their customers. Especially if they did not actively subscribe to a mailing list.
Imagine the outrage if you would by a game on Steam and the developer (not Steam) would suddenly email you. It's unprofessional and in some countries it would be illegal. Even if someone might interpret parts of the tos to mean something like that. I have a different interpretation of what those tos parts mean.
But this is not relevant what we interpret the tos to say. I am not that familiar with Californian consumer laws. AI tells me, it is extremely crucial to ask for consent for a marketing mailing list subscription at the time of purchase and not hide the mailing list consent somewhere deep in the tos.
It might or might not be in clear violation of CCPA. But it is clearly against best practice to not give a checkbox at purchase time to opt out of a mailing list.
That law is from 2020, and I would guess that feature Itch has there is older.