This is not an accurate statement. Mears does the driving, but Disney is ultimately in charge. Disney has a lot to protect in terms of brand and value, si it's Disney running the show.
Also, the old independent Mears system was dispatched and run very differently than DME. Delays were much more common, average waiting times (like waiting for a bus to fill up, which DME does NOT do) were longer, and satisfaction was much much lower.
Mears is certainly involved with DME -- they do the driving. Even aside from the luggage component, which by the way is a WONDERFUL little perk, DME is not just Mears with a different name and logo.
The other nice perk of DME is that once you check in at the DME Welcome Center (on your arrival), your room is held for you if one is ready. This means if I check in at the DME desk at MCO at 10:00 a.m., and you landed at 9:00 a.m. and arrive by town car or rental car at the RESORT at 10:01 a.m. and there is only one room (of the type we reserved) available, I get the room. I saunter in to the lobby at 10:45 a.m. and get the room, and you're still waiting (if no OTHER rooms became available since then) even though you showed up at the resort before I did.