That could be true and makes sense for repairs on boats to use epoxy. Plenty of extra strength and small repairs materials would be cheap. I do know for sure that they use polyester for the new stuff. All the fiberglass supply sites I linked above suggest polyester repairs and polyester gel coat instead of paint for repairing boat holes. And when you start getting over 80mph, that kinda leaves 99% of the boaters behind! That starts getting into the high performance realm which starts begging for epoxy.
Car bodies do very well w/ polyester if the bracing is properly designed. I built the one piece, tilt hood of my Willys from polyester/mat, no cloth form a 'glass mold I too from the original hood (photos of it in my journal) and it is 15 years old and still going strong. A few small cracks but that looks authentic 60s gasser so I leave them there!