Depends somewhat on the level of play- JV, MS- many of those kids are in la-la land more often than not. Some don't even know what number they're wearing, especially early in the year. If the snap is imminent though, you need to flag it.
Varsity play comes with tighter expectations. If it is an interior lineman, it's usually going to be hard for me to get them to scoot back so they're probably going to get the flag.
FWIW, and it doesn't work
ALL the time, but it does,
a lot. Before the snap, as loud as the situation dictates, a general, non-specific warning , "Look down the line" consistently generates corrective movement that eliminates a lot of needless fouls.
It also serves to alert any Coaches, looking over your shoulder, that you at least attempted "corrective officiating" to try and avoid problems, and serves to "reduce" needless comments (not always, but a lot)..