Oh yeah, that's right. When I was a young man back in the `70s I cleaned pools in LA and every morning a bunch of "Pool Men" would be at the chemical supplier's loading up their pickups with crates of gallon jugs of chlorine and acid.

We all knew not to mix them of course, and as a rule added them at opposite ends of the pool near return lines so they'd disperse quickly. The risky part was if you got clobbered in an accident, but I never heard of that causing a spill that mixed the two. I do recall being told there was a law requiring them to be separated, but it was never enforced that I know of.

I have no idea of what they do today, but I'd be surprised if they still do that.