I think, if you ask nicely, they will. Can't say for sure though :P
Obviously they can't make it automatic (no way of knowing who bought where), and clearly they can't add each and every buyer either (way too much work, plus lack of info), so the only real option is for everyone who wants it to convince them they did.
Personally I pre-ordered S3 from Steam (also have it on TT but it wasn't a pre-order here) and I do have access to the forum.
Originally Posted by jeeno0142
I think the DVD with the Steve Purcell slip cover was a perk for all those who preordered with Telltale directly, so it seems only fair that you can't get it by preordering through steam. If you really wanted it, now that you have the game on Telltale you can get the duluxe edition DVD which will not only get you the Steve Purcell slipcover, but loads of other things at $15.
I already ordered the DVD :P
I did think about it, but those extra goodies really don't appeal to me, and the only thing that bothers me with the DVD cover I'll get is the ESRB ugliness... $15 to remove that, no thanks :P