As for the argument that it would be silly if you’re 1mm short: that goes for all sorts of distance measuring. If your shooting range is 15cm, but you measurement gives 15.1cm, is shooting allowed or not? BTW, this also applies to variable distances.
Well I agree, the range is not that precise, but we are not saying that every bullet/arrow/javelin stops at precisely 15cm. We are saying that the effective range, the range that a significant number of projectiles will hit and cause damage to a formed body (or whatever the particular target is), is below 15cm. After that the particular characteristics of the weapon is not worth factoring in to the calculations for the game. Yes, you could day that the boundaries between effectiveness rates are gradients rather than cliff edges, but we are working with practicalities that reflect reality rather than tracking every projectile.
The charge situation is different. The unit will at some stage run out of puff but an officer would in most cases be able to control a charge to arrive at the enemy in decent order and a few yards would be neither here nor there (particularly depending how you think charges worked and how you resolve them in the game – hence the agreement with you about it depends on the mechanics of the game). I understand that the boundary between blown and in good order could keep getting extended by this argument and I don’t want to see charges going on for miles but 1cm here or there seems a little rule mongery to me. The breakdown in distance ‘chunks’ is fairly arbitrary and it seems odd to me that someone who is 15.1cm away would get blow to smithereens and someone 14.9cm away would hit the enemy untouched. If that were the case – time for some tinkering with the rules to my mind.