It's definitely not "BS" it is a debatable subject, The fact that LPS don't ingest phyto in the tank is absurd, for the sheer fact that they are filter feeders and if there is phyto floating in your tank then they are ingesting it. That's not the debate, the debate comes from, "do they benefit from these free floaters?" Some researchers say "yes" and some say "no". Do they accidently capture it and store more than they need? Or do they take this extra phyto and put it to uses? I can’t answer this question with fact after fact.
From experience I dose concentrated phyto and since I started I have had great results with my LPS (frogspawn, favia, and trumpets) they really opened up, colored up and started to grow pretty quickly. Not to say they don't benefit from meaty foods as well, about 12 months later, after reading more on cyclopeze I started target feeding them this as well. And they really took off after that. Was it a combination of both or can I get the same results with just cyclopeze? The 12 months of not target feeding and dosing tank with phyto would suggest no. Will you get good results without dosing phyto and only target feeding meaty foods? I would venture to say yes. But the fact that LPS don’t benefit from phyto is ridiculous.
I'm not a marine biologist, just a hobbyist, so to me I don't have fact after fact, just my experience, and from my experience they definitely benefit from phytoplankton.