That's one of those things that would need to be user adjustable, like grain absorption. Losses vary depending on technique. Just tossing the hops in the kettle or fermenter vs. using some sort of containment, and whether you leave the containment in when transferring to allow most of the liquid to drain. I'm sure there are some other things that would make differences as well.
In the past, when I just tossed hops into the kettle, I had 2 equipment profiles that include extra volume for losses due to hops, using .15qt./oz. for volume loss. One is for 2 to 5 ounces, and the other for more than 5 ounces. Now I bag all of the kettle hops and leave the bags in to drain as I transfer to the fermenter, so the loss is negligible.