This sounds very cool, Gonzo! I'm usually more of a glass half empty kind of a guy, but I feel like encouraging you to look on the bright side of what they're asking you to do. Hopefully, this will go ahead, it'll get the green light, and you'll have at least a writer credit for the feature adaptation of the short you created. Not bad! Or, are they going to ask you to do more than write it?
Provided they're legit and above board and some version of a best case scenario does happen and it gets made etc, I should think that it
will not seal your unhappy fate as a reluctant writer.
Maybe it'd just be like you've said you've already been doing: not writing for the love writing, but because you had to do it in order to have something to film. Sounds a lot like what you're already doing with your shorts. Uh, sorry to be repetitive. And with the added professional cred' this could give you, hopefully it will only place you in a better position to do more of what you really want to do...like perhaps direct something someone else writes.
Although...I've always thought writer/director has a nice ring to it, to say the least.
And, I gotta think that even if no film comes from this, hey, good experience building, right? And, even if they end up passing on this one, they have your name, your resume, they already like your film...maybe something else will click from this down the road.
Also, I think it was Wheatgrinder who recently said something like:
networking: just do it! Paraphrasing, of course.
Rootin for ya!