I have a sneaking suspicion that the seals were modified around the time of the Series II cars. It does seem that more Series I than II people complain about this, but that could be because a) there are more Series I's than II's (especially Imports), b) the Series I's are older and the seals have suffered more over the years.
I had a look through the parts CD and I think the part was changed around that time - perhaps Mike (Feeney) could double check, becuase if that is the case then I think he will have a small deluge of people buying new seals !
On U.K. cars the seal was changed (at least part number-wise) in 04/92 (a bit later in Japan). There is no guarantee that the part was modified for improved sealing and, as far as I can briefly ascertain, no technical bulletin is available. Did this known problem come to light during the production run of the U.K. cars? Probably not.
All weatherstrips ordered now would be supplied to the new pattern as the old part numbers supercede to it. I've never had the two side by side to make a comparison, but if a Series 1 owner and a Series 2 owner were to find themselves side by side at a meeting, a comparison would be useful!