I agree. I'm a profesor in the first year of the University of Buenos Aires. We have no official list of answer for the exercises (but there are a few unofficial ones).

The students can ask me or the TA abut the exercises. We prefer to see what the student has attempted, and find the exact spot where the student made the mistake. It takes more time, but it's more helpful than a nice ideal solution.

We also may recommend to make another exercise from the official list and come back in 10 minutes with a solution attempt, or make some custom exercise on the spot that is about the same subject. (Exercises about derivatives are easy to invent, integrals and linear algebra is harder.)