This seems like a fair criticism. There are two parts to a typical bond transfer,
1) Owner #10 must create and sign a well formed BOND message to Owner #11
2) Owner #11 must create and sign bitcoins to Owner #10
They are done as part of the same transaction. P2P bonds are based on smart property, this page has detailed protocol descriptions that may make things clearer:
https://en.bitcoin.it/wiki/Smart_PropertyYep, SIGHASH_ALL was the bit I was missing. Looks 100% possible to do this, indeed.