Hi Janice,
The original text you highlighted referenced independent publishers. So I assumed that was who you meant when you said "But some do require you do buy a minimum number of copies."
Here, you are saying "some major big five" publishers are now requiring it.
Whether independent or a traditional big sixer*, ANY TIME a publisher asks the author for money, or to buy copies of a book, etc etc, this is subsidizing costs, and so I'd call them a subsidy publisher. "Trad publisher who's asking you to buy a few copies" just seems too sneaky!
Do you know who they are? I know publishing has gotten tough, but it's hard to imagine the greats stooping to this.
*
https://www.idealog.com/blog/introducing-the-north-american-big-six/#:~:text=The%20Big%20Six%20is%20a,Hachette%20Book%20Group%2C%20and%20Macmillan.