Expansion Anchor Re-torquing

I have dealt with a couple of projects involving Hilti's Kwik Bolt TZ and TZ2 expansion anchors. Once the anchors have been installed and torqued, it was requested that the anchor be completely loosened and the nut/washer removed so that the fixture could be modified in some way and then the anchor be re-torqued in the same hole. My understanding is that this is not permitted, but I'd like to know for sure what best practice is for this type of situation.