So I have it. It does increase his protection pool but it does also seem to recover protection even without Jyn. I have seen this when running him in P3 AAT without zJyn lead where he basically lost all protection but then started to slowly gain it back.
If you read the character strategy it clearly states that he recovers protection when hit.
I'll try to back this up in GW tomorrow if I get the chance.
For the record I also have zJyn lead which is the obvious place to use it but I would say there are much better zetas.