I have not heard many people supporting the use of WD40 as after run. It's a good solvent but a poor lubricant and not as effective as after-run at corrosion prevention. It is good for blowing cr@p out of buried engines.

I agree though that it makes little difference if the after-run is methanol soluble or not - it doesn't need to mix with the fuel; just needs to prevent corrosion. Petroleum based oil tends to stink a bit when you crank the motor up next time, though... And you get lots of white smoke. Marvellous!