Yes it's a bit confusing since most people including me often talk about "forward mids" which in this case is referred to the opposite of recessed mids, above neutral level boosted mids in the same sense of often using the term "bright" to refer to boosted highs. I think this "forward mids" could possibly use another word to describe it like for example "bright" is pretty obvious what it means (or what it sounds like it is). However when I refer to a headphone sounding very forward I mean that it sounds like I'm in the center of the band/orchestra or whatever playing with the singer very up-front and the closer sounding to me the more forward which to me leads to a more engaging experience. That it's forward sounding DOESN'T have to mean the soundstage would be worse, but more often that becomes the case if everything sounds more centered. With very laid-back presentation it sounds like there would be a distance to that "center" of the band/orchestra, like you're sitting further away.
XB500 doesn't have what I'd call forward mids or bright highs, more the opposite, yet it's very forward sounding, everything sounds very up-front, like I'd be on the stage with the band or possibly being on the dancehall in a club when listening to electronica etc with music surrounding me. I haven't owned very laid-back sounding headphones, DT770 Pro/80 and Denon D1100 are only gently "laid-back" sounding but still everything sounded further away like there was always a distance to the singer etc and I wasn't standing in the center of the music, more like the experience you get sitting further back in the rows in a concert. The JVC HA-M5X I picked up is even more unbalanced than XB500 with further recessed highs and more recessed upper mids (but slightly more forward lower mids) but it's even more forward sounding than XB500, probably as forward you can get in a headphone I'd say. For example playing Unreal Tournament 3 it was very obvious when the girl announcer's voice was heard it sounded like she wispered in my ear on HA-M5X and on XB500 it sounded like she'd stand very close to me.
I dislike having a distance to the singer/instruments/band/orchestra or whatever and usually end up selling headphones quickly that aren't forward enough sounding and yes like I said earlier I don't even like aggressive sound signature where the mids and highs are boosted and screaming into my ears. I rather use terms aggressive, bright (cold), dark (warm), veiled etc to explain frequency response balance related things, in another thread this was what forward / laid-back what it was explained to me that it was related to the "distance"/positioning in the soundstage as I previously had mixed some of the terms. Anyway whatever you should call it, that's what I personally mean with those terms.
Because when you think about it, how do you explain how some headphones, for example AKG K518DJ, XB500, HA-M5X that have both recessed mids and highs are very forward sounding if it worked like that if the whole frequency range would be boosted and therefore must sound "forward".
Provide me some proof about laid-back and forward is what you refer to then. 
