How would that be a useful comparison? Aren't the use-cases too different?

Not only is the moon >100x farther away (even accounting for near-horizon satellite angles), but you're also trying to bounce a signal off it as a passive reflector, which is harder than just transmitting something an active lunar receiver could detect and re-transmit back.

If starlink were anywhere close to as far away as the moon, you would have a comparable antenna size. That's like bragging about how compact your zoom lens us while your buddy trying to get photos of the Martian canals.