No explanation required or given. There are reasons to be FOR or AGAINST ethanol. My main objection to ethanol is the lack of CHOICE. It has been forced upon us prematurely.
FACT: ethanol contains LESS BTUs per unit than gasoline.
FACT: ethanol DOES attack some plastic and rubber compounds.
FACT: ethanol absorbs moisture from the air. This causes phase separation which leads to a short shelf life .
The damage is real. Your statement that you never had a problem does NOT invalidate all other claims of damage. I have seen many engines on outdoor equipment have varying amounts of ethanol damage - from no damage to extensive damage. For some reason, some equipment tolerates the ethanol better than others.
Given a free choice, the ethanol would disappear as it has in the past when marketed as an "alternative" fuel. I do remember the "gasohol" of the 1970s. And again in the '80s. This time it is force fed to us. I still like to have a choice in the matter.
Oh....back to the chainsaw....
MOST fuel available when that saw was built was unleaded. The last of the leaded fuels available for on-road use were pretty much gone before 1980. Is the saw older than 35 years????