Usage of Rotary fittings in this manner okay?

[India48]

As long as it is not the G1/4 threading that is rotating, and thus breaking the o-ring seal, it should be fine, its situations like that that rotaries are designed for. You could probably test this by tightening the fitting whilst the case is open, and then close the case, and then check that the fitting is still as secure. Alternatively, by the looks of it, you could also look at the case front on, through the empty 5.25" bays, and watch the fittings as you close the case door, you should be able to see if its the rotary component of the fitting that is moving, or if its the G1/4" (knurled part) that is.