Fred - IMO that's a very different thing. Common-naming relies on the fact that propagation as we do it yields two pieces of the same individual's genetics. A year later, you can take those two pieces - and they will grow back into one individual colony.
Another of the same species + coloration - will not likely grow back together with the original.
I find such names to be useful, as in our local area - we can refer to these names and see if we've traded the same coral with the same guy. I know for sure I wouldn't need another blue tort - but Ereefic's blue-tort-like unique coral ... while fairly similar to the standard blue tort - is a different coral, that will vary differently.
Given most of us can't/don't go through a formal, complete ID practice ... we're left talking in generalities. IMO, non-scientific naming allows us to refer to specific individual corals, which with today's trading and wide sharing, is useful so as to not trade for corals you already have - and to differentiate some that are similar to each other.
I have a piece of `Green Slimer' and a `Bali Green Slimer' that are two different species of Acropora - yet if all lumped as `green slimer' without further differentiation, would give very confused people as different corals are being referred to. IMO, it's important to keep `names' with the corals, as well as to not have folks naming similar corals by the name of an already known variety. And - I wouldn't have two if they were named the same ... but by having a difference, even subtle, it allowed me to know they were two different corals even though as 1" frag, it didn't look that different. Grown out, there's zero doubt.
Yes, naming can turn into marketing. `Rare' is not a common name, IMO
But either we call them just about nothing [purple acro #1], or we call them by incorrect scientific names [Acropora tortuosa, when actually A. gomezi], or we call them by reefer-names [green slimer, cali blue tort]. IMO - the third is the best option, though none of the options are ideal.
Growth form, one tank's coloration - IMO this is not what is referred to. Just as we could get clones of the same dog and raise one lovely, and one mean dog from the same genetics. But - that doesn't mean another dog of the same variety shares the close genetic bond of the clones + an equivalent close bond.
IMO, that's what's going on with `named varieties'. In such cases, we are naming a specific genetic individual strain. Will it look the same in all tanks? Nope, nothing is guaranteed - but IMO there's the potential of the same exact coloration. With another genetic individual, it might be similar, but exactness IMO is worth paying attention to.
Just my take, go ahead and think differently if you like