I said the same thing. Not a coincidence.

No coincidence. Mine started after my Covid-19 vax in May 2021 and I went all summer in a lot of pain not knowing why. Then, in August 2021 after my second vax, I went into the full PMR mode of pain from the neck to shoulders, to arms, to hands (had to wear splints), hips, back of buttocks and thighs, and was not diagnosed until Jan. 2022. PMR does not run in my family, nor any other related disease. Never had these symptoms before the vaccines and despise my decision to get them, even though we were forced into it. I will never get a booster.

Not a coincidence at all. PMR is triggered by a virus. In my case it occurred with 1-2 weeks following a case of Covid-19.
A recent study states PMR is a common side effect of the Covid-19 vaccine. I don't see why a flu shot couldn't also be a trigger.