One big reason why IBM has the freedom to do this now is that they sold their PC division to Levono. While they had that PC division, Microsoft wielded the big stick of saying, "Your PC licensing costs just went up." But now IBM sells nothing that depends on getting Windows licenses, so they are pure customers. And if Microsoft is selling at a bad price/performance point, IBM can walk.
I'd wondered about that when they originally sold their PC business. But then had forgotten about the idea.
Cheers,
Ben