For what it's worth, my pool builder also installed my IC60 on the wrong side of the Pool/Spa actuator and didn't give me a full 18". I argued for him to do it right and I got all this, "We never do that, you don't want to chlorinate your spa, just use the spa return in pool mode, don't overchlorinate." I showed him the instructions and he was dismissive, I also showed him how Pentair automation does NOT allow more than 20% IC setting in Spa mode for the exact reason/concern he had. He sort of ignored my request for a couple weeks, but when he asked for "Pool Startup" check, I said, "I'm still waiting for my IC60 to be installed per Pentair's instructions, once done I'll consider start up complete". His plumber was there in 30 minutes, it took him maybe 20 minutes to re-run.
Gotta hold your ground, now that it's spa season, I'm really glad mine is installed right!