I still don't get it.
In earlier editions your movement
was spread out over the entire combat turn.
In SR5 it happens instantly, when the player decide to move, during the player's action phase.
-
just like it would in a board game.
Yes, you can burn all your movement in your first action phase - but then you would have no movement left and you still have to spend your free actions on "running" for the remaining of the combat turn (but you would also get -2 dice on your ranged attacks unless maybe if you have a gyromount, get +2 dice on all defense tests and everyone get -2 dice to attack you with ranged attacks until it is your turn to move again in the next combat turn).
If you want to move after you already burned all your movement you would also need to spend a complex action to take a sprint test to move a few meters during an action phase later in the combat turn (but ranged attack against a sprinting character get another -2 dice).
This is an edge case.
A more "normal" case would be that your player move maybe 5-6 meters (considered walking) in the first action phase and -depending on agility- a few more meters in his second combat turn. A
melee character -or a ranged character with a gyromount- would probably want to always "run" (agility x 2 meters or more) from his first action phase and onward because of the defensive bonuses (and really no cons).
Most people have two IPs. Really wired people have more.
If you
average out how much you can move per IP then wired people would move slower

(it worked in SR2 since back then wired people got multiple action phases -and oppertunities to move-
before everyone else. In SR5 everyone move in the first IP even if they are very slow... wired people in SR5 get to act a few times
after everyone already done their movements)
I simply don't see why you should not just stick to RAW. Shrug.