485RFE for medical TB test, any previous experiences?

In the RFE, I was asked to provide TB test. I am pretty sure I have done X-ray before but didn't do the skin test. However, as far as I know, TB test usually can be done by both skin test and X-ray. If skin tested positive, then go for X-ray. However, for foreigners who had vaccine in the childhood, skin test would be very likely positive. Usually doctor just skips the first step (as it's NOT required by USCIS) and do the X-ray only. As long as X-ray tests negative, it would be fine, which is the case for me.

So I don't know why USCIS still ask for TB result. It's very ridiculous to do such an unnecessary test. Did you see others receive such RFE as well? Or does USCIS changes the rule again?