What are you talking about? Anytime you are doing a conventional wash with water that is capable of spotting, you want to keep the car wet at all times (until it's time to dry). So if I'm using a foam gun and a rinse bucket, I will hose some/all of the car off with water, then foam the section I'm going to wash, do the contact wash, and move on to foaming the next section, etc.
I am not a user of the foam/ rinse/ foam / single bucket method. However any videos I've seen the person doing the contact wash foamed the entire vehicle and proceeded to contact wash the entire vehicle. Only rinsing after entire vehicle was contact washed. Foam each section as one goes seems to me to be a very inefficient process. Way more so than moving buckets around the vehicle via the two bucket method. That's what I'm talking about. Have never seen it done as you say above.