Miche Primato BB smooth... until torqued?

Just wondering if anyone else has noticed this recently, maybe it's a batch thing, but I have had this with a coupla Miche BBs, the standard Primato 107mm track jobbie with loose cups. Out of the packet it seems buttery smooth as you would hope. Grease everything up and install it into the frame, torque it up nice'n'tight, and suddenly the spindle seems a bit stiff and no longer silky... spins OK with the cranks on, but when turned by fingers without cranks you can detect a tightness that wasn't there before. Doesn't really make sense when you look at the construction, unless that groove that has been discussed previously actually allows some compression of the outer races, with no coresponding play in the spindle to allow for it... thoughts?

would rather have it a little tight than the cups coming loose which they are prone to do

+1 that, just baffled as to why? The bog standard Sugino 103mm uses the same construction other than the r/h cup is an interference fit on the bearing, but it stays smooth however much you bend the wrench. Not natural, it ain't!