[Warning: Most of you aren't going to like this and rightfully so. You'll see why if you read on.]
This could be to fulfill a very specific tactical role. From what little I can tell, Belfodil is big, works hard, but has some technical ability to go with it. [Here's where it gets bad.] I remember reading something from a Stoke supporter talking about Stoke's best football under Pulis [told you it was going to be bad] and one of the tactical quirks he mentioned was that they used to play with a sort of "false 10", a target man who played a little deeper than the traditional target man forward position (basically man-marking the opponent's defensive midfielder), whose main job was the hold the ball up, win headers, and create space for the proper striker. Of course, as the Premier League got more sophisticated, it became near impossible to play this sort of player. But then last season, we saw a new model in the form of Troy Deeney, someone who could win all of the physical battles and hold the ball up, but who also had the quality to get on the ball and find his strike partner (which made Ighalo look incredible).
We know that Walsh has had at least a passing interest in Deeney (he was linked heavily with Leicester before Walsh left and was even with us tenuously). So maybe this is Walsh's ploy to get a Deeney-like player, someone who can get a hold of longer passes to get us up the field but who also has a touch of quality to set-up Lukaku or beat his man 1 v. 1 and create a favorable attacking situation elsewhere. I know that's not very inspiring and that, all things being equal, we'd rather dominate possession but we need some way of getting a foothold against some of the better sides in the league while we work on what we do with the ball. (Or maybe Koeman is just Dutch Pulis.)
So yeah, this isn't anywhere near what I'd hoped we'd do in this window. But I guess we just have to trust Walsh's process for now.