If we now report exact hold times of each intermediate hop to the sender, it might allow them to re-identify the receiver, breaking the BOLT12 privacy gains we just finally introduced. But of course, if we consider this case, we’d also need to think about mitigations for the onion message parts of the protocol.
For the blinded part of the path we don’t have to report hold times (the forwarding node knows if it’s part of one). Also the sender does not know which nodes make up the blinded path, so cannot assign blame / penalties anyway.