I ran into a pool room owner in California back in the early 90s who was BCA certified (he had papers on the wall to prove it); and he swore you couldn't masse a ball without raising the butt of the cue above your shoulder. I masse'd the CB around a full ball and was nowhere near my shoulder and his response was that's not a masse. He was full of little truisms like that--absolutely clueless. Not knocking the proven instructors or their certifications, just saying they're some out there--"instructors" with very little knowledge, forget about playing. I learned libraries full of information from a couple of road players that "adopted" me when I was learning who had no certifications other than their battle scars.
There are tons of certified instructors out there that are well worth the money; but I think you need to network a little to find the good ones.