It's just for general scaling reference nothing exact, because in-game they're all shorter due to their animations, and they all have the exact same size bounding box for world collisions. I picked engy because he is one of the average sized characters, along with sniper, demo and pyro. Among those, I picked him cause engy is my favorite and when you're in Hammer you are 'engineering' your map.
If you really want a different one you can change it yourself, just look at the picture I posted a couple posts up.
and yeah, about the ropes. You really want to have the exact origin marker model so you can align them precisely.