What it means to me: Someone is going to pass me on my left, so don't move that way. It's OK if I stay where I am, or I can be nice and move to the right (if there's room).
The two guys should not have been riding abreast (well, let's be real, I'm not going to judge them for doing it), so one should have dropped back to let you pass safely (I am going to judge them for not doing that).
Machismo (whether by men or women) is an ugly thing.
What irks me is when there's a multi-use path and people are walking as far apart as they can, one on the right and one on the left. (There's a painted yellow dashed line in the middle, so it's clearly directional like a street.) I came up to a couple a while ago, slowed down, and yelled out, first, "Hi there," to see what they would do. They stopped and moved farther apart, so I continued, "Um, passing, um, in between, I guess."
They probably still don't know what I said or what they should have been doing, but that's the price you pay for a nice multi-use path. I'm just glad it doesn't have a speed limit!

