rank positions

I've been looking at implementing search result document navigation in velocity for WLUK, and wondered why in the XSL we take the rank of a document (document-info/rank) and then use it to create two new params (epos and spos), both of which are passed on every search result link, and both of which are ignored apart from using them both to create another variable called position - which is also passed around! Is anyone aware of a reason for all this? I'd like to just replace all 3 with rank - and only rank.