No Tilt, this isn't about troop bunkers at a base.
As you surmised, it's about map room hardness but controlled by a new strat factory that I've called a "city" for lack of a better name. This is an idea for creating a strat target that is reachable, non country crippling, not a milkrun trough, and clearly significant toward the "win the war" effort. The effect needs to stay local to an area, not global imo.
Volron, the way I see it, if the zone master base, the one the "city" is tied to is captured, then yes, all the other bases in that zone would only require 10 troops instead of 30. This makes the zone base have real importance as well.
This is also in keeping with htc's continuing progress toward making base capture more difficult.