And if you 'don't know without a chrono stage,' how the heck are YOU perceiving that they're downloading, hmmm?
Answer: By the visible recoil and noise, of course, just like I do.
You can't hear or see 100 or 200 fps, nor can you hear or see lighter bullets.
If SASS shot poppers or falling plates, that would make it obvious, but they don't.
Whether or not your club "downloads" isn't really the point - SASS does not mandate a PF, so there is no incentive to shoot full power ammo.
On the contrary, for those seeking to be competitive, there is significant incentive to shoot light loads.
That's not a bad thing in itself, but I'd be a lot more impressed if SASS mandated a minimum PF.