Are you suggesting PhD candidates have AI write their theses? Or just writing LaTeX commands while the students write the core text? Because if it's the latter, LaTeX usually isn't the bottleneck.
No, I am not suggesting PhD candidates have AI write their theses. The original poster implied that they typed latex code for their thesis out by hand, to which I responded that it seemed silly to do so, silly in a similar way that taking a horse drawn carriage would be vs using a car.
So, do they write their formulas like S a b f(x)dx in their hand-written source text, but then get the LLM to convert that to \int_{a}^{b}f(x)dx? Invent their own "markup" to indicate S a b is the integral from a to b? They might as well learn \int and just use that.
I write LaTeX by hand all the time whenever I need to put any math in my notes, and depending on your use-case or field, you learn the LaTeX for that which you use often and it's faster than trying to use most tools.