I've started watching Enterprise and noted that T'Pol's eyebrows aren't those of a typical Vulcan. Here's an image of her in season 1:
Note how here eyebrows don't point upwards like a typical Vulcan's would, but are more like human eyebrows. I thought that this perhaps might be something to do with the fact that she is a female Vulcan, but then I thought of T'Pring - compare the two:
You will note how T'Pring's eyebrows are pointed upward much more than T'Pol's do, more like a typical Vulcan.
I also note that when I do an image search for T'Pol, there are images of her with the more typical Vulcan eyebrows, for example:
My question is why aren't T'Pol's eyebrows like the typical upward-pointing Vulcan eyebrows in season 1? I'm looking for an in-universe or out-of-universe answer.