This makes less than no sense to me. If you make the assumption that DL's perspective on the int'l front cabin has always been to: a) protect BC revenue potential without exception at all costs, and b) sponge back in SkyMiles at the highest rate possible to control the inflation that they themselves created.

This would do neither. It would provide no incentive for even an incremental revenue driver in the front cabin (even a co-pay scenario on DL's existing insane non-LUT rates would be more effective), and it would have a marginal inflationary effect on SkyMiles because of the few people who DO subsequently book into Y hoping for the best. (Which, amongst DMs, will be precious few.)

If this turns out to be true, with that particular precondition, then I think it's safe to say that this is nothing other than a PR move so they can point at something and say "See, we listened!" while missing the point entirely...