I've disabled the checkbox many months ago and it's still disabled today. EU citizen, not sure if that's relevant.
> Allow your content to be used to train our models, which makes ChatGPT better for you and everyone who uses it. We take steps to protect your privacy. Learn more
Could be worse I guess.
Edit: I have a pro subscription now but it has also been on a free tier level for perhaps 1.5 of these years.
At best they’ll “anonymize” the data before adding it to the corpus.