That is correct.
In November 2012, Disney designated some companies as 'Preferred' or 'Featured' provides.
Those companies are allowed to drop off and leave scooters and other medical equipment at Bell Services for guests to pick up. They are also allowed to pick up equipment left there by their customers.
One of the big reasons was the huge numbers of companies Disney was having to deal with; by choosing 5 vendors, it is easier for a Disney to deal with.
There is not anything special or superior about the Preferred vendors compared to the ones that were not chosen; there are many good companies that were not chosen to be one of the 5.
There is more complete information in post 2 of the disABILITIES FAQs thread, located near the top of this board.
All other companies need to make arrangements with the guest to drop it off and pick it up directly from the guest. Some people have chosen to use one of the Preferred vendors so they could have the
scooter waiting for them.
But many choose to stay with the company they have used before and found the direct contact was really not an issue for them.