We'll see how this settles down. I've been Hyatt Diamond on and off for three of the past seven years, with SPG as my main program.
SPG has basically copied what Hyatt used to give, which is continental breakfast in hotels where there is no lounge. Except that (1) Hyatt offered it as well as the check in ammenity and SPG offers it instead, (2) SPG is offering the option to choose the non-lounge breakfast even if there is a lounge, (3) Hyatt offered a full continental breakfast, which in hotels with a buffet meant everything cold plus oatmeal and toasted items.
Hyatt's old policy still meant uncertainty from hotel to hotel about what would be included, how big a credit would be offered toward the full breakfast, etc. You were never quite sure what would be on the bill when it arrived. SPG seems to be in the same situation, but worse as the buy up option will not be universal, from reports so far the credit is sometimes derisory, and the continental option will not always be served in the restaurant or offer the full range of cold buffet items.
Hyatt obviously recognized the problem, because about two years ago it changed its policy. Now Diamond members get full breakfast (buffet or any menu item plus beverage) for everyone registered on one room. With two children that benefit can be worth 100 USD a day in the nicer US hotels, more in Europe.
It seems like what SPG is doing here is aimed at checking a box on the comparison chart. But unless implementation is improved it will hurt itself in the long run by causing frustration and uncertainty to its customers.