They needed to boost the Apple Watch adoption when it was released. To do that, they wanted many apps on there, including popular ones like Uber (and Uber is actually a good use case). Unfortunately, WatchOS couldn’t render maps back then. The marketing department was probably at their ass to get it working, so the engineering team had to come up with something so Uber would be on the Apple Watch: they allowed them to use private APIs.

A very bad move but I can understand the motive

Hmm... I suppose that does explain the motive, though I'm not sure about the logic.

On the other hand, I have the luxury of Monday quarterbacking and the knowledge of what has gone on between now and then.

I am curious as to who else might have gotten that entitlement and we just don't know it yet. Apple, being more privacy aware (or at least PR aware), probably has not handed it out to bunches of people and governments. Probably...

Only Uber got it.

Are you certain of this? If so, how?

I investigated the situation and checked to ensure there were not other apps using this (As to not unfairly single Uber out).

I think this is how the Find My Friends app on the phone draws its map to this day.

/s