It is very tiring to hold back the shot in a position like that. In real life you just wouldn’t do that. And in general your archers know their range and will/should start shooting as soon as they have a target in range without any orders.

The volley fire thing is from black powder musket/rifle days. Basically volleys were used so you can actually seen what you are shooting at (aim) and manuever (hard to move while reloading. Easier if everyone reloads at the same time). Most armies still had small groups sharpshooters/snipers running around the field and taking shots freely.