Actually, they aren't completely the same. If you look (you'll have to squint to see the fine print), but the "executive rooms" (which are the ones with the access to the lounge), come with use of a robe and slippers (you'll probably be able to keep the slippers if you want them, but not the robe. ) You may also get some upgraded toiletries as well.

Basically, the upgraded room is the same thing as getting a CL level room at any other Marriott hotel. So this hotel isn't doing anything different than virtually any other Marriott with a CL. The real question is if a hotel were to have only CL level rooms available, should a Gold/Plat have to pay for that room (even though they would normally get that as a free upgrade) or just pay the standard room rate?

BTW, I know that Starwood will make a Plat pay for the upgraded room if that is all that is available, even if that Plat could have received it as a free upgrade. So Marriott isn't doing anything different that their competitors in this case.