Old thread, I know, but for more current readers doing a bit of research (or like me, trying to refresh my memory ...):

The single-ring cranksets were generally intended for track use, so no weather-sealing (the primary purpose of the helical grooving) was really required since most outdoor tracks are pretty much unrideable in the wet and it was never a consideration on indoor tracks, obviously.

The same distinction is currently made on the Pista BB - there are no external weather seals installed, unlike the road square-taper BBs.

It's also worth noting that the post C-Record road sealed BBs have true ISO tapers wheas the current Pista BB retains the pre-ISO, Campagnolo proprietary taper - and as such, there are frequently problems with the current Pista crankset being mated with a 111mm road BB unit - the taper is not quite long enough on ISO spindles so the back of the LH crank comes up against the scallop where the spindle transitions from cylindrical to square section - this can and does cause radial cracking to develop, away from the corners of the square broaching in the crank.