That's the way Roland did it, that's the way Korg do it. I guess, if you wanted to, one button could do it ALL, with double taps. But it is simpler, and less confusing, if there's a button for each function.

Generally, you hit Record to start the recording, then you hit Play to go into the loop. But if you need to play a bridge or something before you need the loop, you hit Stop. Then you hit Play when you needed the loop. And either Record to start a new loop or Stop if you wanted to go to you being in control.

Mostly, and with screen real estate being a non factor, I'd go with what is the simplest route. Plus, it's what they are used to doing.