I think that people's tolerance for simple metaphors is related to their level of curiosity. I'm pretty sure that many people would be satisfied with a "rubber band" explanation even though it doesn't fit. The more curious person though would probably, as Feynman said, want to know why rubber bands behave in the way that they do, and then the metaphor would break down.

This to me tells me two things about Feynman:

1) He was a man of great integrity

2) He wanted people to be more curious about the world