The UK video I posted has some details, 15,000 balls per hour doesn't seem that slow to me[1], and still, according to the video, they are putting the clean ones into "netsacks".
Most probably when they have the sacks full there are not that many "dirty" balls remaining in the pit and they can put a separator of some kind across it to start putting back the cleaned ones.
Found the site of the manufacturer of that machine:
https://ball-pool.eu/services/
What I doubt is more that the cleaning is actually done on a weekly basis or so as recommended.
[1] I have no idea on how many balls are in the "average" pit, but the US video is touting 80,000 as if it was an extremely large one
