There is no number of specific stories that should convince anyone, unless there is also some indication that they are being evenly sampled! You would have to compare all of the stories of men who were denied appointments to make a conclusion. To get a probability from a count, you have to divide by something.

I mean, isn't the fact that there were virtually no women in academia back in the time a convincing enough proof in itself that there was, indeed, discrimination?

Discrimination on the part of gatekeepers isn't the only thing that can keep minorities out. A culture that tells them not to try doing it because it isn't their assigned role, a fear of being the only one of their group among a majority of another group, and earlier discrimination that prevents them from getting qualifications but isn't the fault of the gatekeeper could all be responsible. Given the information I know and what has been brought up in this discussion, University mathematicians could have been perfectly willing to hire women.

This is just the good old pipeline fallacy all over again.

The fact you like to call it fallacy doesn't make it one.

How do you know that last part? What was the state of education in Germany at that time? What was considered the qualifications for professorship at that time? How many people of any gender had those qualifications? Do you have any specific knowledge about any of this?