Question on R2 mechanic

[DaveASA/FED]

Ok speaking NFHS, I was trained to not mirror the R1's signal on a net serve, show the point toward the team but don't show the net signal, still not sure why, the whole cause I didn't see it I don't get...(was watching the recieving side and didn't see the fault I understand....but if I'm doing my job right I don't see 2 hits either and I mirror their signal for that but that's another topic) but my question is that is the only signal that I do not mirror correct? Example if a serve goes out of bounds untouched, I mirror the out call correct?