yes and no.
if its not intended to keep the animal for the forseable future, why keep it in the first place ?
if its to keep temporarily to outgrown our tank , why keep it ?
I agree with you on the tangs : but DEPENDS on the tank. some tangs are open water swimmers, they cruse long distances - for example Sohal's, Lineatus, Naso's... you can see from their bodyshape.
Other tangs, like Kole's, Xanthurum's, Flavscens swimm lot less and need therefore much less swimming space / aquarium.
Nonetheless, a Sohal should never be kept something less than a 180g or similar, LONG tang. a 180g cube or tall tank wont cut it.
Im all in favour of education.
Everyone BEFORE every SINGLE buy, you must read what you can - and that REALLY RESEARCH about the fish , coral or whatever animal you are buying.
But giving out "so-so" information is what I critisize.
Heck I have 3 clownfish books. I'v bred them. I know their scientific names by heart. But in a couple of weeks I'm going to add a pair ( well , wanna be pair ) of Perculas to my tank.
I've spent the last 4 or 5 days reading everything about perculas.
In reefkeeping, you never ever ever know everything. Always something new to learn.