Seriously. Why don't they at least cut the back of the nut so the string is in line with the peg? That can't cost a lot extra...
You can fix that easy enough...either with nut files or a bit of sand paper...but TBH, I'm not sure how much they really need to be "in line", because no matter how much the back of the slot is in line, there's always going to be an angle because of the front of the slot. The string has to make an angle to go from slot to machine head.
If you just file/sand down that edge of the nut slot so it's a bit rounded/smooth...it will be enough. You don't need the slot angled.
I've done that on all my guitars. I just picked up set of nut files for my string gauge, and it took no time to both cut the nut depth correctly where it was too high, and at the same time smooth out that back edge a bit.
There's probably more friction at the bridge saddles, even though they are in line. I like to take a 400-600 grit paper, fold it, and then run it through each saddle slot until I feel the grit on the paper has worn off...which is pretty quick against the metal saddles.
I also will sharpen a #2 pencil to a fine point, and then just work that back-n-forth a bit into each nut slot and also the bridge saddles...and that graphite will keep things smooth for awhile. If/when I sense a string hanging, I'll just repeat with the pencil.
Right now all my guitars hold tune real well after I touched up the nut slots with the files...and then treated them and the saddles with some pencil graphite.
I play pretty hard, but once I get a set of new strings settled in...they all hold tune.
Now..that don't mean that #$&% G string is playing nice...
it's always a PITA, but overall I can work with it and just adjust my string pressure as I play to adjust pitch...plus, for leads, a little vibrato goes a long way to fixing the G string issues.