Injecting into an area that has become firm: why not to — does this still hold?

Asking directly, because I could not find a straight answer: Injecting into an area that has become firm: why not to — does this still hold?

I have read the maintained page on this and I still have a gap, so I am asking rather than guessing.

Context: retatrutide, 7 weeks in, currently at a dose I reached by the standard four-week steps. Everything below is my own record rather than anything a clinician told me.

The specific question is the one in the title. What I have already checked: the labelling summary on the relevant documentation page, the two most-linked topics in this subcategory, and my own notes from the last 13 weeks. What I could not find is whether the answer changes at higher doses or whether it is the same arithmetic throughout.

If the answer is "it depends", I would rather know what it depends on than be given a number.

Injection discomfort: comes from needle gauge (finer = less discomfort), volume (smaller = less discomfort), temperature (room temperature or warmed is less uncomfortable than cold), and technique (smooth, purposeful injection is less uncomfortable than hesitant). All four are under your control.

post #2 answers the question as asked. The question underneath it is different.

Angle of injection: 90 degrees into pinched tissue ensures subcutaneous placement. It is not always necessary and shallower angles can work, but 90 degrees into a small pinch is the safest technique to learn first.