So you by "control" you mean also the AI-controlled units to which you can give some simple commands? I don't buy it. FOTS apparently(I haven't played it) lets you control 40 units in one stack. Napoleon mods(DarthMod Napoleon for example) have 40 land units and 30 naval units as a matter of fact. All evidence and this includes statements of designers that it's difficult to control such big armies, the inclusion of the Tactical map, the reported ability to let the AI control some units of your army and issue simple orders, all evidence suggests that you will be able to have stacks of forty units. Oh and the unit icons will become progressively smaller the more units you have.
So no, I don't think you're correct.
As for unit size, if you look carefully at Jack's Vidcast, around 0:41-0:45 you can see a unit of hastati. They're 25 across, 7 full ranks and an eighth rank of five men for a total of 180 men. Just before that you can see a similar unit behind a wall, three deep and with a very long front.
So at least for now it seems that the frontage is not very small.