The C1 C2 adjusting is totally different from the usual chiro adjustments.
I went to my chiro for many years and many adjustments , he was very precise and gentle. He also had many patients and none that I talked with had any thing like a stroke happen.
I sometimes think that stroke talk is a old wives tale that get passed around.
I'm sure there are good & poor chiropractors, same as with doctors, mechanics, plumbers, any service provider..