Well, the short answer is no, he’s wrong.
The longer answer is that he could be right..ish: lets say that you started your tank with all dead rock, dry sand etc I would say that it could take up to a year before you could keep more demanding acros etc due to the fact that your tank won’t have the needed stability needed for a decent amount of time.
some very experienced reefers can get away with doing this and adding acros after a month, but they are the exemption, not the rule.
If a random dude decides to throw a spathulata in to a new tank like this it will strip in no time at all.