Doesn't make any sense to me. Look at it this way, on a MTB with a 22 tooth granny and 175 mm cranks, a 200 lb rider is going to produce 700 lb of tension on the chain while climbing. Those chains don't break much, if ever. You will not be able to come anywhere close to that chain load with typical fixie gearing. A wider chain may be a better choice, but the narrow is more than strong enough.