Hex shown onHover on "Unknown binary data" when signing is incorrect

[fabioberger]

When signing this message with parity signer:

0x3bd03be584f9df8a79ed49d8502c63d5fcff148157544242ffdbcc2b64321b1e

I am shown the following hex when hovering over "unknown binary data" in the Parity Signer UI:

0x292fc53642b56f05f1655c0903f6316df200dcac006fa3005d616ee948e9755a

When I'd expect to be shown the result of:

keccak256("\x19Ethereum Signed Message:\n" + len(message) + message))

which is:

0x21c78f55e3f54ab5d872bfea03ad05d7bfb3d35dc1a537fd3ae731cdbb9bea21

If I disregard this discrepancy and sign the message anyway and verify the v, r, s values with the personalMessage I expected to be signing, I can verify that it is in-fact the message that was signed. The signature is valid for the expected value.

Why is this other hex being presented to the user? Where does it come from?