My native-US-English speaker read:

“disappointed that the Pro tier was opted-in to training on prompts by default” [and required manually opting out]

“the Team tier was now also opted-in by default” [and required manually opting out]

In context of each sentence and the larger comment, read smoothly here.

Also - have seen more than one lively discussion on these phrases, since defaults can stick 95% of the time and Big Tech has done their best to be abusive about what they automatically enable for users by default for some time.

It's understandable but it is technically inconsistent and dilutes the meaning of opt-in. Opt implies an active choice, so you never are opting for the default.