Blood Elves ARE High Elves and vice versa.
Void Elves are a mutation.
The reason this is an important distinction is because Void Elves are judged different enough to qualify to be playable.
IF Void Elves are one flavour of High Elf, then there is a difference.
IF Blood Elves are similarly another flavour, then they are distinct from High Elves.
Which means, if you follow the logic to the end, that High Elves can be playable. Which is of course the real agenda behind this particular debate. Playable High Elves. Again.
This logic is shutdown once you understand the context of the question Ion was asked, which was (to paraphrase) 'what about High Elves?'
High Elves ARE Blood Elves and are playable. Void Elves are mutants, another flavour, and are playable.
But because High Elves are already playable they are not adding them again just because some people disagree with the faction they are currently on.