I mean it not as a 'fixed game starting position position' - I could probably have said 'get forward, more advanced' instead. My personal belief (not based on any hard evidence) is that a red arrow doesn't change an MR to an AMR. It makes him more eager to get forward.
For example: a 3-5-2 with red arrows on the wide men is not an 3-3-2W-2 which has no arrows (in my mind). In the 3-5-2 example the MR with red arrow will try to get forward (and possibly into the space an AMR would be in).....but he doesn't start as an AMR he is starting as an MR. Whereas in the 2W example the AMR starts as an AMR so in the same time it takes MR to move up, he will have moved forward too. In other words an MR with red arrow and an AMR in a foot race will start at different points but the MR will run quicker.
I'd be able to explain it better if I counters on a table that I could move to show you.