I just tried to vote to close the question How to measure the energy consumption class of a home appliance? because it is squarely about engineering and not about physics. However, it told me something like "questions with open bounties can't be closed". That seems like a odd rule. A bounty doesn't change whether something is off topic or not.
Perhaps the point is that it would be wrong to force the bounty to be wasted, but if that is really the intent then the bounty could be refunded when the question is closed. Actually in this case I think it could be migrated to EE, but that doesn't change the fact that it is off topic here.
Is this a unintended interaction, or is there really a logical reason behind this that I'm missing?