The difference is SPG has "Last Standard Room Availability" where Marriott has "No Blackouts". Marriott has never forced hotels to offer ALL their available standard rooms for awards. Instead they do force hotels to offer some "%" of standard rooms for awards every night (i.e. no blackout dates). Though they do give each hotel the ability to pick some number of "nights" and reduce that "%" of available award rooms to a smaller number. Less than the normal % required but more than 0. Marriott (nor any Marriott insider) has ever disclosed what those %'s are.

Years ago Marriott did have an option that came close to the SPG "Last Standard Room Availability". Back then the % of standard rooms available for standard awards was actually smaller than it is today (i.e. they could offer fewer standard rooms for awards each night than they have to today.) But to balance that Marriott used to offer "Stay Anytime" awards which could be used for any available standard room (i.e. last standard room availability), but those awards cost a lot more points per night than a regular standard award. Do a search for "Stay Anytime". There were a few discussions that included both Marriott Concierge and a high level Marriott insider, Socrates which provided us a bit of an inside look into the program. AFAIK, Marriott has not changed the program around standard award availability since then (at least not in any major way, though it may be very possible they have tweaked the %s, up or down, over the years.)