I dont think it matters as long as the fig has the look you want.
I've got a bunch of shield maidens in my latest warband, and GA crew with female heads on.
Those shield maidens are some tall ladies

So unless you're playing the game with your head on the table and have them all lined up next to each other you really dont notice that much.
and if their all lined up i think you're in for more problems than some being taller than others

.
Also , as you get older your eyesight isnt as critical as it used to be and at a distance you have trouble working out which one is a specialist
and which one is just a normal soldier let alone a 3 or 4 mm height difference ...

Roger