The POH means exactly that: a factory pilot has demonstrated that the aircraft can be landed with a 15-knot crosswind. They did not test any higher crosswinds, probably because they were not required to.
What happens if the crosswind is higher, you try to land anyway and you bend the aircraft? This depends on what's written in your insurance policy, and what's in there is typically copied verbatim into club rules and such. My club, for instance, mandates a maximum crosswind component of 15 knots (despite the fact that all our aircraft have a demonstrated limit of at least 17 knots). If you land with a higher crosswind and cause damage, you're the one to pay for it.