I call bullshit. Anybody can leave Twitter and Facebook at any time. Some don’t only because they don’t know how to operate otherwise. That ignorance is not evidence of platform dominance.
To be clear dominance is where one player owns market majority. That is not Twitter. There is lots of evidence on this. Twitter might dominate Truth Social but it still lags far behind Facebook, TikTok, and probably Instagram.
Vendor lock-in is where the cost to switch to an alternative is supremely expensive, such as rebuilding infrastructure from the ground up. That is radically different than the stupidity of not knowing what your options are.