Encroachment Philosophy

[Welpe]

This is primarily for high school and below. I know that encroachment restrictions (except for defense touching the football, touching a player on the other team and being the neutral zone to call defensive signals) do not begin until the RFP and the center touches the football. I am curious though how everyone enforces a player lining up in the neutral zone?

For example, the offensive huddle breaks, the center touches the football and then a wide receiver lines up in the neutral zone but realizes it immediately and backs up. Is this enough to call it or does it have to be very blatant such as the receiver being oblivious to the fact he is in the neutral zone?

Thanks!