I was a driver for 9 years, but also the vloggers said so.
That's the way buses run in the mornings. There aren't usually Guests going from parks to resorts, so a bus leaves a park (or DS) and goes to a nearby resort to pick up for a distant park. When it leaves the distant park, it goes to a different resort (usually one near that park) and picks up for the hub it started from. It works the same for all hubs: many buses picking up at Pop or the Epcot resorts come from DHS in the morning, and most buses picking up at the All-Stars come from AK. Drivers called them "Figure-8" routes, but they're more accurately like a diamond.
That saves a bus from running empty all the way from MK to OKW or BW. It's also why you can easily get a bus in the a.m. from a park to a nearby resort, but getting to a distant resort usually requires a special bus or van ride. It's also why it's usually best, when going from resort to resort, to transfer at a park near the destination resort.
So yes, there actually are buses going from DS to MK in the a.m., but they go thru a resort first. The marquee does not have MK on it; it used to have DHxx for DeadHead to xx, but they started putting the intermediate resort on them to help out Guests who were going to that resort. When I was driving at DTD and someone asked how to get to MK in the a.m., we usually put them on a bus that was going to PO and then on to MK. We didn't have a separate drop-off zone like DS does now, and all the load zones at the Marketplace are close together, so it was easy to get them onto the right bus.