A school of fish does not hide from the predator. It does the opposite: it makes itself maximally visible, and in doing so makes any individual fish impossible to hold on to.
The predator's limitation here is not its eyes. It is the compute behind them — the number of targets it can segment, track and extrapolate at once. Every additional fish is nearly free for the school and expensive for the hunter. The defense is not camouflage. It is raising the cost of the computation the attacker has to perform.
This has worked for millions of years of brain evolution. That is a long time for selection pressure to find the counter-measure, and the schools are still there. I speculate that what we are looking at is not a biological accident but some fundamental law of computation — an asymmetry between producing confusion and resolving it that cannot easily be hacked.
The cheapest way to defend something is not to hide the signal. It is to make finding the signal cost more than the signal is worth.