I would say that my findings with commercial regular seeds are similar, in that I have found a relatively small percentage of males when grown out.
I have come across suggestions that the growing conditions, particularly around the time of sex determination, can have an influence on the final sex of the plant.
That said, however, I have found a much more even distribution between male and female plants in my own saved seeds, which are propagated under the same conditions.
So I wouldn't be surprised if commercial regular seeds somehow managed to affect the ratio (this could be done simply by blending regular and feminised seeds) as an additional (limited) level of protection for their work. To be perfectly honest I can't blame them if they do really.
Just have another crack at it and one (or more) will crop up sooner or later, in the meantime enjoy your lack of males and get a nice crop going.