Well there's a difference between Shcherbakova being a world champion that isn't an Olympian because she hasn't yet been able to compete for an Olympic vs. Tuktamysheva who has already had 2 opportunities to compete for an Olympic team spot.
For me, Liza is precisely the type of athlete who should be training a quad. Unlike a lot of women who train quads, Liza has more or less mastered all the triple jumps. When she does miss a jump, she can usually hold herself together for the rest of the performance, so she won't be too reliant on a quad to earn a high score. Most of the American women who train a 3A or quad can't even do a 7 triple LP cleanly, so they're not able to get the full benefit of the added difficulty unless they also do the easier elements well.