I disagree with that. It really depends on the cause. As I wrote I lost every sps in my tank due to rtn/stn. I suspect the rest would have been fine if I just removed the affected monti instead of blowing it clean.
Some parasites also seem to cause it.
Stn and rtn wasn’t the cause… when you figure out what caused the stn,rtn most likely a alk spike that’s the issue.. it is not contagious, I promise you! There’s very old sps tanks that just get a ghost every once in while and everything else is just fine.. I’ve played that game many times over 20 years of keeping sps.. I just lost my asd rainbow Millie to stn while 60 other acros are flourishing and growing at record pace! Never changed a thing and the tank never skipped a beat. I’ve been scraping my montis lately to cause rtn cause they’re over running prime real estate and no issues at all!