Hydraulic lifter preload...who really checks this?

Yes. Make sure you have some preload, and make sure you’re not bottoming out the lifter plunger. Everything in-between is fine. This is what a hydraulic lifter is supposed too do.

Back when you could buy good hydraulic lifters, guys that were pushing the rpm limit would set the pre-load to zero and gained a few hundred rpm without concern of lifter pump up. I don’t think anyone is doing that with today’s hydraulic lifters.
Still being done. We do it on 602 crate motors all the time.