For coral health, I observe that keeping alkalinity reasonably stable is much more important than calcium being stable. I’ve had calcium up to 600 ppm and did not notice any impact on my corals. The corals also seemed unaffected when I got calcium down and stable around 425. I concluded it didn’t matter much.
Being a kalkwasser user for decades and an AFR user for years now, raising calcium has always been true for me for the reasons Randy states. It’s normal, expected, and generally not a problem. I dose solely based on alkalinity demand.
To put in perspective, I maybe test calcium once or twice a year and test alkalinity at least weekly and sometimes daily when I’m changing something.