Why would they care how players are playing their game? Did folks using the same troops cause the developers personal pain or cause reduced sales? Yeah, it does sound like selling a problem as a feature. What they probably wanted to avoid is making players walk all the way back to replenish troops, but knew they had problems with all the walking.If I remember correctly, they have been clear about this troop limit in developer's videos, the purpose of this troop limit is to force players to try different type of units throughout the course of the game rather than just rely on a few favorite low-level ones the whole game.
Just a note: reading this thread had me go back and fire up KB: HotN - the only one I never finished. They have ways in multiple games to get players past using the same troops over and over. In this one, they just take away all your troops and make you start fresh with human troops. There are also limits on how many you can buy.
To the point - I always play the KB games the same way, or fall into a pattern - I try to never lose troops. So I'll build a group that has healers, offense, plus a hero with talents geared towards avoiding troop loss at all costs. I don't like traveling back to getting new troops, but it's also just how I like to play the games - I don't reload if I lose a troop, but it makes the battles that much more interesting. If the game were balanced so I couldn't avoid losing troops, but had to walk around and re-supply after every battle, it would make the game even more horrible.
Resupplying troops in KB was just annoying enough that you didn't do it constantly, and were willing to go into fights at lower strength while you felt you could, also the best units were limited so it hurt losing even a few Jarls or such. A mechanic that added dimension to combat. I think if you add the ability to just resurrect troops after every battle, a significant portion of the game falls apart.