I don't like AOS, but I do think this is an interesting rule. I wonder if they had done something like this for WFB back in the day, if it would have helped spark interest in the game. I have see some weird things involving flank attacks and so on where I was like, in real life, the defender wouldn't have just sat there and been pounded on the flank. The strict rules on moving, the facing of the unit, and all that, I think it made the game complex. This removes much of that. I guess instead of rank bonus you could just reward based on the unit size or something.
I really wonder what would have happened to WFB had they not destroyed the old world, but changed the mechanics to allow troops to move like this. Of course, moving around 20-man units one model at a time would also be annoying too. But I think this makes a lot more sense given the scale of the game, than the rank and file WFB has done.