ECM replacement - starter runs during reprogramming?

(mid-90’s Buick) Someone I know had an ECM injector drive output go bad. He got a replacement ECM online, but had to take it to a shop (not a dealer) to get it ‘initialized’ (If that’s the right word.)

He says that, to do this, the tech had the ignition switch in the ‘run’ position, and during the entire 20-minute process, the starter motor ran. I have no reason to doubt his report, but I find it kind of astonishing.

My question is, why would they run the starter like that? All I can think is maybe to ‘characterize’ the engine. But, it doesn’t seem like they’d have to do that for 20 minutes.