Are you saying that the bus waits at the bus stop at CBR until more people come and fill up the bus? It's been a year since I've stayed there, but that was not my experience at the time. In fact, I was always under the impression they keep the buses moving so the next bus could pull up to the stop.
FWIW, the typical advice is that you should bus to MK since it drops you at the gate. If you drive and park, you will need to take the monorail or ferry from TTC which is an additional wait/line and can be congested at park closing. But if you have gear like strollers or wheelchairs, it might be easier to take your own car. Just depends on your situation.