Women are required to meet a higher bar in part because it's assumed that two men meeting for coffee are meeting for business, but it's less clear what is going on if a man and a woman are meeting for coffee.
The relationship between trust and a character trait of trustworthiness is not necessarily straight forward. If people think you simply aren't in a strong position to hurt them, they expect less of you.
Women are often in a position to inadvertently harm a man without meaning to do so. Important men often want no appearance of impropriety. This makes it unclear how a woman can even establish a trusting relationship to a man.
Sometimes, husband-and-wife teams work as an effective in for the woman. Her relationship to him helps establish intent for everyone. It helps prevent muddy Waters in that regard.
If a meeting over coffee reads as a date if it's mixed gender, it may not matter how trustworthy she is. It may only matter that he doesn't want there to be talk, so he won't meet with her.
I attended GIS school in my late thirties. It's a two-thirds make field. I have a strong math background and argued with one of my professors that his math on the board was wrong.
He said "I bet you lunch." right before realizing I was right and saying "I feel a lunch coming on."
He was probably around 50 years old. He didn't really want to be seen buying lunch for a relatively pretty, young female student. After class, he quietly thanked me for standing my ground and correcting him and he slipped me a twenty dollar bill to cover lunch.
If I had been male and we had actually gone to lunch together, this would have been an incredible networking opportunity. But we never did have lunch together because he didn't want any appearance of impropriety, even though he respected my mind and appreciated my class contribution. It wasn't enough to overcome the question of "What will other people think?"
Of course, that story and conclusion involves a lot of inference and assumption on my part. Maybe he would have slipped a twenty to male student as well and not actually eaten lunch with them.
And that's part of what makes it so intractable. If I accused him if excluding me based on my gender, it would only deepen the rift, not bridge it and I can't actually prove it's a gendered thing, which makes women look histrionic when they complain about things like that.
And, yet, we continue to be subtly shut out. And I think this is a major way in which doors just never open for us.
If you can't even have coffee in public with someone for fear of what others will think, how on Earth do you even begin to network and get known well enough to establish a name, get referrals for work, etc?