No idea why but I find the same with my cyc x 'Gambas' (which surely comes from asturiensis) has perhaps a dozen per pod and all fertile while the reverse cross gives me lots of rubbishy stuff and only a couple of decent seeds in each.
After thinking the 2 bulbs Betty Clark gave me, of tazetta ssp. patula (or ochroleucus) were not going to flower, I noticed yesterday there are 3 buds so I should be able to show those later this month.
There are quite a lot of 'Nylon'/'Tarleton' types out and seedlings from my (not quite) 'Julia Jane' but what I have as cantabricus ssp cantabricus I'm sure is not. I've had two importations from Tasmania in successive years, each of 6 bulbs, and the whole lot have varied between pale cream and light yellow, not a white among them. I have hopes of Rafa's seed in dur course.