They didn't check Tau 44 as ZOI, they just checked it as a mineable zone. Though yeah, it's up to the CR to say if they can mine there or not.
However, the Zephyr thing is not the CR's decision, to be fair here.
Just because hardware is sold in that guard system, does not mean the owning faction can deny ship sales to properly ID'd and tagged characters.
That would be a gross violations of the server rules, as stated in Faction Rights and Responsibilities.