That last boost about Sudoku reasoning, where you have 3 cells with 3 identical possible digits = they'll go nowhere else in the box they're contained in is good for solving "hard" or 4-star and 5-star puzzles.

It's still not good enough for "superhard" or "diabolical" puzzles; what make those awful is that they'll have cells with 2 or 3 swappable pairs and one or more of those pairs would be "don't care pairs"--which preclude simple trial/error method of solving if you have just one "don't care pair".

A "don't care pair" is a pair that will be correct regardless of which way you write them in.

It's more helpful to master quad sets and "X-Wing" method of solving.