It makes me wonder if the new Worgen fur colors might be cut customization options from Shadowlands that initially went unused due to the original limitation of how every Worgen customization option had to be linked with a Human one (REALLY glad they managed to fully separate Worgen form and human form customization).
Scars as their own options was an idea that came relatively late in development of Shadowlands, which is a fact that could explain why the scars are baked into the Worgen fur color options instead of the scars being a separate option. It may or may not be possible to separate the scars from any fur color textures depending on the source files and their availability.
There are a number of customization options that were intended to be rolled out for Shadowlands that never made it in, including some that were shown off at Blizzcon 2019 like proper brown eyes for Humans, eye shape options for Humans, and a body/face paint color for Trolls.
There may be other technical reasons for not having scars as a separate option as Dracthyr completely lack any scar options at all, though for the Dracthyr the current lack of scars could have been just a time constraint due to all of the other art assets that needed to be made at the time.
I personally hope they are exploring the idea of expanding scar options to all playable races, especially with the blind eye options now being available to all races.