As mentione above its Rev's thats causing wear.
If your engine revs to 18,000rpm then it will almost certainly wear quicker than one revvin to only 5500rpm. The lubricants have to work harder and sometimes become less effective and something spinning/scraping/opening/closing at higher rpm's will wear more and be more prone to stress failure.
So NO a 2cyl engine does not wear more than a 4 cyl for the same conditions.
Anyway, its proven that most engine wear occurs at startup, due to the lubricants having drained away from where they are needed the initial few revolutions can cause the same amount of 'wear' to engine internals asa many thousands of miles of use at proper operating temp etc.