Completely true, that. Ive seen exactly as you said with 4 friends of mine when I helped them go over to Linux. On the Win11 side, they didnt even KNOW that they clicked a button to sync their files to some cloudshit account (Onedrive). There's no proof either way, but their files were exfil'd.
But with the horrendous performance and scam behavior, Ive heelped others to Linux to really good effect.
Just theres that 1 person who *needed* Windows and all the abusiv behaviors it inflicts. It was more akin to "Executives dont get fired for recommending IBM/Microsoft", and a utter refusal to try something better. Theyve been a friend for 2 decades, so I gave them the warning, but did help them.