The fibers are not the limiting factor here as far as I understand. What starts to happen at 0.3%, according to my literature, is the resin matrix starting to de-attach from fibers crossing the load path. John Shuttleworth does also mention the 0.3% limit but does not explain what happens in the same depth and only mentions onset of micro-cracking of the laminate.
Last year I did a little reverse engineering of the bow and twist limits we use for printed circuit boards (built from glass-epoxy prepreg) and it turned out those limits correlate with the 0.3% strain limit of the aerospace indu