Floating the voltages is a well known protection scheme; it used to be the norm before the advent of inexpensive GFCI outlets, and is still used in bathrooms in Europe and on naval ships, etc. It IS safer than a solidly grounded neutral due to fault tolerance; if one phase suffers a ground fault, it simply changes from a floating system to a corner-grounded system. Fault clearing is diminished, though; if there's a ground fault, you might never know until a 2nd fault occurs.
I'd just never heard of portable generators NOT bonding the neutral.
