As I have just today become a Norton Commando motorcycle owner again - (sold my '71 Commando in 1978), I was doing some internet research. The early Commandos, like my old one, had fiberglass gas tanks. In 1970 the company found that the fiberglass resin was breaking down for some reason. After a bit of research they determined that the resin was not compatible with "certain additives" used in gasoline. They then (slowly) switched over to steel tanks.

So this problem was noted at least 35 years ago. It's interesting that it apparently hadn't affected boats until now.