Technically legal, although the intent is to use pilotage as well as instrument nav. If you're just on radials or vectors you're missing the training value. Obviously don't make any mention of IFR, IMC, or hood time for that flight in your logbook.

I cannot guarantee that a rogue fed would not have a different opinion, so I wouldn't advertise the fact. I think you would win in the long run, but best not to fight the battle at all.