I think they mean if you're a woman (trans or cis), it can be terrifying to meet with people. At least that's how I interpreted it.

Edit: Perhaps they are also talking about non-binary people, which is why they chose the words "not male presenting".

In addition to what the other posters said, even merely being a skinny twink (insufficiently male-presenting) is dangerous in some places

People think they are male when they see them.