Wow, Breya doesn't trust Tagon's Toughts at all. Because seriously, personal connection or not, that restriction is aimed at them. Unless ... Int-Aff-Int screwed up somehow.
Breya's not saying that the Tough's can't visit... just that they can't bring PTU hulls with them when they do it.
At least two of the boats from that battleship's complement are non-PTU hulls, and those would probably be allowed to continue deeper into the Sol system, so the Breath Weapon can act as mothership from her current position.
I can think of a couple of reasons for this new policy...
1. Breya doesn't want giant unstoppable teraport cages inside her perimeter.
2. Breya doesn't want to be constantly chasing pirate fleets away from the PTU's.
3. Breya doesn't trust hulls she can't easily scan through.
4. Breya is trying to file a diplomatic protest about long-gun technology.
or, worst case scenario:
5. Project Zeus is a method for firing superweapons THROUGH teraport cages, effectively turning any sufficiently robust teraport cage into a pocket battleplate. And Breya doesn't want any disguised foreign pocket battleplates entering her star system, especially when Project Zeus is too secret for most of her traffic controllers to be warned about it.