What are you talking about? That isn’t what they said, and a ball doesn’t have a widest point. That’s more or less the definition of a ball.
The distance between the two poles is smaller than the distance from one side to the other following the equator. The earth isn’t quite a ball, it’s a bit squashed because of way it spins
Degrees aren’t a metric unit, actually. Gradians were an attempt to make a metric unit for angles, but nobody uses those so it didn’t really work.
The people who designed and will use this telescope will be using “steredians”, which is square radians. That’s the unit which astrophysicists use for describing an area of the sky