When a penalty flag is thrown, a considerable amount of information needs to be relayed to the Head Referee. The acronym we use is T-I-N-S. The official that throws the flag needs to report the Team, the Infraction, the Number and then Stay with the head referee in case he/she has questions. The last element is eliminated insome cases at the CFL level due to their headsets (usually for downfield officials), but many times additional information is required as well.
For example, as you pointed out,the point of foul is important on some calls. Some penalties are applied from point of foul or line of scrimmage or sometimes either…whatever is more advantageous to the non offending team. Sometimes the gain on a return can decide the application. Sometimes an official has two penalties (Cdn officials do NOT throw their hats to indicate a second foul like the US guys). On no yards, it can be either 5 or 15 and that needs to be communicated.
And, officials have great distance vision but are 50+ in age and you know what happens to your reading vision when you hit that age…can you imagine an official putting on his cheap assed readers to punch up the tiny keyboard on his watch?
So, for the time being, speaking with the referee is probably the best, albiet low teck way of dealing with flags.