Show me the data that tells you the small increase in extremely small particles that does make it through an oiled filter is harmful. "Common sense" tells us that dirt (in this case, airborne particulate matter) in the engine is bad. Why? Where is this (very small) grit going? Not in the oil, the seals around the valves and piston rings prevent that. Score the cylinder bores? Sure, maybe, if the dirt is harder than the liners, which most airborne PM is not because hard stuff that is big enough to cause problems tends not to stay airborne for long. The vast majority of crap that gets through your filter (and it's getting through the stock filter too) ends up combusted and/or blown out the exhaust. I bet the people in Iceland with K&N's had to remove and wash theirs along with the rest of the poor saps with paper filters, difference is they didn't have to buy a new one.
Blowing dirt through a shop vac onto a damp piece of paper is flimflam just like putting a pingpong ball in a tube with a couple filters at the bottom and a fan at the top. Salesmanship cuts both ways and I'm not buying what you're selling.
Fact is, I've used K&N's and similar oiled filters on every vehicle I've owned. Never burned a drop of oil or gotten less than 100k out of any of those engines. Fact is, thousands of others have had the same experience.
As for where the gains happen with a filter, that depends on the engine. If there's a restriction at the air filter, it won't only be beneficial at the top of the rpm band, it will be most beneficial wherever the TORQUE PEAK is, and less so in other places. The S65 peaks at 3900rpm and maintains a fairly flat torque curve to 7500rpm. That's not the top of the RPM band, that's, well, 50% of it. So, if there is indeed a restriction at the air filter on these cars (I've seen enough dyno charts to believe it's not a figment of our collective imagination) then it's not just going to help the car at or near redline, as you claim.