Correct. I'm not sure what the question was. Taking a shot though...
When you buy your first Company of a Formation it's considered the Command Company. If it's a Legendary Formation that comes with any special models (Heroes, Banners, etc.) then they must go in this Company. If it's a Common or Rare Formation then this Company is where you will place any upgrades ( Captains, Banners, etc.) you purchase for the Formation as well as (usually) any Epic Heroes that join the Formation.
Just think of it as saying "you need to keep all your upgrades in the same Company". You can't put your Captain in one Company, then a Banner in another, etc.
You probably also notice that nearly all upgrades are the same across armies. This is on purpose. Upgrades are pretty consistent on what they bring ( an Orc Banner == Gondor Banner == Elf Banner ) so there's no reason to have them cost different.
