This is just describing pruning though, the whole purpose of better pruning methods is reduce size without compromising performance on the intended task.

If you are embedding the weights of a model in an FPGA then the size of the FPGA is your bottleneck, it's unlikely to be your bandwidth talking to the ground because FPGA's just aren't that big relatively speaking.

Yes ground comms is a factor, but realistically A. How often are you going to be flashing new models onto your orbital systems relative to B. How much inference are you going to be doing with any one given model, and C. How big is the amount of data you'll then need to beam back down to collect those inferences.

Is the upload of the model weights really the dominant factor here?

By all means, strive to make the model as small as possible. But there's nothing special about the edge device being in orbit compared to it being on earth but hard to access.