The recomendation for the provider implementation at
http://java.sun.com/javase/6/docs/technotes/guides/security/crypto/HowToImplAProvider.html#Step3a
specifies that engineWrap and engineUnwrap methods are optional and
a SPI implementation might not implement it.

If these methods are not implemented then the java.lang.UnsupportedOperationException
is thrown by the defult implementation of these methods and as result it is thrown by Cipher.wrap()/unwrap() methods.
But UnsupportedOperationException is not specified in the list of the
Cipher.wrap()/unwrap() exceptions.

I think that this exception must be specified.

Other unspecified behavior is initialization of the Cipher for WRAP_MODE/UNWRAP_MODE mode if the wrapping of the keys is not supported.

What kind of exception it can throw? The specification does not define it.

Probably the UnsupportedOperationException can be defined in the Cipher.init() methods too.