Buying used - question about something Carfax says

Looking at a used 2016 GMC Acadia. Carfax says one owner, shows as a personal lease.

Weird things that I don't understand:

1. Why does it say a one owner vehicle when there a pre-delivery inspection followed by a lien/title reported, followed a few months later by a title update, followed two months later by another pre-delivery inspection, followed two years later by another lien/title reported? Almost looks like it was actually bought and sold several times. How can that be a one owner vehicle? Was it a lease vehicle that kept being returned and reissued to a new person?

2. There's an engine/power-train computer/module check done twice about 2,000 miles apart. Does this signify a problem? We tried to call the place that was listed as having done the work but can't get through to them.

Any of this concerning? It's a Carmax car and they will not let us inspect before buying so we have to buy, inspect, and then return if it's no good.