No, it means that being a father (negatively) influences your ability to be a successful founder. Like any other barrier, this can be overcome.

To get to the question I think you are trying to raise, it does seem like gender has a non-zero effect on this influence. Even ignoring the fact that, for likely cultural reasons, mothers tend to spend more time with their children, being pregnant itself presents something of a (short term) barrier. Again, it should be quiet possible to overcome this barrier, but not by pretending it does not exist.

Undoubtedly, one could make a case that being a parent is actually a benefit towards being a successful founder.

> for likely cultural reasons, mothers tend to spend more time with their children

I don't think men's inability to feed infants is cultural.

I don't think anyone pretended it didn't exist. But you oversimplify when you say it's only negative. Learning to fly planes or raising a puppy by yourself has a nonzero effect on your time too, but usually these are considered pluses when hiring someone, because they show responsibility, well-roundedness, maturity, fulfillment, etc.