Hmm…. it doesn’t seem like there’s a downside for Bob to lie, and there’s definitely an upside.
devrandom
1

Indeed Bob can prove that Alice is using old data, but he should not be trusted for more than that. This feature is just an additional safety net, worst case scenario we go back to where we were before.

Also, it’s easy for Alice to periodically assess Bob’s honesty: at any time she can announce an old commitment number and see what Bob answers.