I may be waaaay off base here, but I did take 6 years of horticulture in high school (just loved working in the greenhouse for personal reasons). I seem to remember that in some plants a seed or two could come about even if no pollen is available. These seeds wouldn't be viable, and they would be very scarce. I don't know if this applies to cannabis as our ex-hippie horticulture teacher would refuse to answer questions regarding such a subject. He did, however, have a keen eye for spotting the seedlings after their post-seed-leaves emerged...