I think this is simple really, If you want SPR with HBM2e you buy it right away, yeah? You have no unlocks in your future. It's no different from buying a top tier server cpu from Intel today. Only thing is, if you can only afford a cpu with limited features, Intel gives you the ability to unlock more features in the future. This is smart segmentation, instead of fusing things off forever; a loss to Intel, and a hassle for the consumer to change a perfectly working chip. Only problem I see here is if intel charges more than the difference between a feature-limited chip, and a full-fledged one, or the next tier, whatever.This is problematic not just from a consumer perspective, but an ecosystem one as well. Now you can't just assume that SPR will support those ISA features, further fracturing the codebase.
This is the kind of stuff that sales folk drool over, but creates real headaches for the customers in the short term and the business in the long. And Intel is in no position to be so callous.