Does it reinforce the continuation of the High Elf story? Or is it a glimpse of the past before they became Blood Elves? Again, a matter of perspective. The Blood Elf heritage questline is a flashback to the events that led them to choose the Sin’dorei identity going forward.
That’s not to imply they are any less High Elves because of it. But the Ren’dorei, and still existing elves who call themselves Quel’dorei are no less either.
If we are going to use in-game elements to justify this or that, one could say that the Darkfallen customization being available to Void Elves lends some legitimacy to their own claim to the High Elf legacy since it implies that some of those who fell (and were raised into undeath) when Arthas sacked Silvermoon, have joined the Ren’dorei. I’m not making that claim. I’m just using it as an example.