I think the latter. I used it for a while then just stopped. Don't beleive the hype, in fact, some fuels, at least the ones available to me at the LHS say you don't need it, that the fuel is non corosive. I take my motors apart often, atleast every gallon, to check things out and never found any rust or oxidizing of the metals. The bearings are the only thing that seem to suffer, but that has nothing to do with the after run oil, it's just the nature of the 35,000 rpm beast. lol A little or alot of WD-40 to blow out the bearings and clean the case real good is all I ever needed. WD-40 is a better cleaner than a machine oil IMO. So all I'm saying is that after run oil is good for 1 thing, assembly. Wouldn't do without it. But as far as prolonging engine life, preventative maintainence, cleaning, and attention to detail will do just as well if not better and be lighter on the ole' wallet than after run oil. IMO of course. If anyone has any thing to add, please please please do. I'm no scientist or said expert, just a hands on guy.
Hope this helped.