For me out of over 100 fem seeds only three have hermed. Two were my fault(I assume)early on as a novice when I didn't have my main flower room light proof, the last was a Grapefruit Krush and it was the only plant in veg out of six that refused to show sex before 12/12 flip, about 1 week into 12/12 it clearly showed the typical clusters of pollen sacs beginning at the nodes.
I chose fem over regular because with regular I may only get zero females out of ten for all I know, with fem I know I will be getting female with a possibility of a herm, most of which come from bad environments. There can be bad genetics now and then but I feel a weekly inspection for herms from week 1 to week 4 of flower is well worth the effort and extra seed cost rather then get stuck with 50% or less females using regulars which is usually the case.
i am not sure of the number of seed plants i have taken to full maturity most likely well over 1000, i do tend to run clones mostly but do run some
seeds along side on each grow, i have never had 100% male from 10 seeds as you stated was possible, i guess its possible, but you would be the most unlucky guy in the world lol
if female seeds work for you that is great, i have nothing against them i do think they are overpriced, but then the regular seeds are not cheap either
many of the breeders and strains i am interested in do not have fem versions, some breeders are against the fem thing, each to their own
i feel safer using regs and they cost less it is more likely a female is true from regs and is not going to give you a nasty surprise 4 weeks down the line
i have kept some fem plants in the past without problems, so i would never rule them out but would always rather run regs
i have no problems removing males during preflower and still filling all the grow space with the remaining females
peace