In Rebels Season Two's finale, Twilight of the Apprentice, it was revealed that Vader has eyebrows, which are missing in RotS & RotJ.
In the old days of the Holocron system, G-canon would override T-canon as in the aforementioned instance. In the present Disney system, however, I'm unconvinced the same approach applies. Further elaboration in the spoiler tag below because it's slightly off-topic, but it explains how I arrived at that belief. You can skip the elaboration if you want.
The override approach allowed tolerance of any contradiction introduced, which is extremely confusing and unfriendly to newcomers to the universe. At one point, George Lucas decided to abandon his prior vision of Star Wars and overwrite it with a new vision. That was how the second, still-canon Clone Wars came into being. This was eventually formalised in Disney's official canon revamp. The new system worked on creating a singular, consistent world with content planned for commercial release decades into the future. That implies no override, and as such "all content are created equal". However, these material in George's and subsequently Disney's new vision have significant differences from even the movies before this vision change by George. One notable disconnect I felt when rewatching RotS recently is that the encounter between Grievous, Obi-Wan & Anakin feels too strongly like a first encounter as opposed to a meeting between familiar foes. Vader's eyebrows is just another difference. If we continue with the movie-over-TV approach to determining canonicity, most if not all Grievous-Kenobi-Skywalker scenes would have to be non-canon for the scene in RotS to make sense, so much so that the Clone Wars can hardly be worth calling.
As explained in the elaboration, I find it difficult to accept that the movies can still be considered to override everything else, such as TV shows, even if they are all Disney canon. My current headcanon, therefore, is that instead of "movies are more canon than television", it's now "the more recent work is canon". I can't prove this to be true, however, but it seems to be the more appropriate policy that doesn't contradict with what Disney retained as canon imo.
Considering that Rebels (which is canon) is produced more recently than RotS & RotJ (which are also canon), can we say that Vader's eyebrows are retconned into existence?