confusing sentence in signal/slots description page

The sentence: "Since the signatures are compatible, the compiler can help us detect type mismatches." on the signal/slots description page is confusing and maybe wrong.
The compiler does no compile-time checking there. At the end it the type matching is done during runtime without the compiler.
I don't know the internals why the signatures are compatible, but it helps for sure the developer to avoid simple type mismatches.

see: http://doc.qt.nokia.com/4.7-snapshot/signalsandslots.html