I am talking about purchasing for myself using my own account on 12306.
There may have been some grandfathering of old 12306 accounts on the verification requirement, but I had to re-set my account recently because of a new passport number. And last month 12306 certainly blocked me from buying a fourth ticket until my passport was first verified.
My passport is due to expire next year so I'll get to find out what happens then. I'm hoping to be able to keep my current account, surely there is a way to update the ID number without abandoning the account (though it may involve a visit to a train station somewhere).
I just logged onto 12306 and it appears that you can change your ID number at any time (perhaps because it is unverified).