[PandaRider]

Not a guitarist (take my comments with a pinch of salt).

Your teachers are both right: Either advices (1) or (2) works as long as the practice is hard.

That said, while (2) may sound easier because the approach pursues "comfort in the mind" over perfection... this is still hard because because by definition: you still need to get from uncomfortable to comfortable!

A similar example in bodybuilding: muscle confusion [1]. To build better squats, one requires both compound(2) and isolation (1) exercises

[1]: https://www.nytimes.com/2020/01/08/well/move/muscle-confusio...

(Huge Caveat: this only applies to physical deliberate practice!)