This is a big nothing-burger as far as I'm concerned. In reality there is no change in how this is working. Maybe some elites were complaining to Marriott that they weren't upgraded to the 'best available room' at check in, which we know rarely if ever actually happens in practice. Hotels were demonstrably not giving Titaniums and Platinums the best available rooms. In many cases you'd be lucky to get a slightly better view, or a high floor, or one category better than you booked.

The change in verbiage just reflects reality and I don't see this changing anything, as hotels do their own thing anyway with how they provide upgrades and elite benefits.