Don't use boat motor mix?

While fiddling around with a garage-sale chainsaw I downloaded and read the old manual. In it I was surprised to read the caution NOT to use BIA marine oil/gas mix in the saw because it doesn't have the necessary additives for an air-cooled engine. I've never seen a warning like this and have been running my chainsaws, trimmers and outboards off the same 40:1 mix of synthetic marine oil/gas for years. Can this cause damage. .. or is this an obsolete warning that's not true for modern marine oils?