In my view, it should be just a HBD KE (because I interpret KE as HP KE), liquid does not count because it can move, and HBD can also, so that's kind of why.

Also, any HBD gained from rewards is actually counted as HIVE rewards for the KE calculation.

But if one would like to make a KE for HBD, then in my view it should be something that contemplates how many HBD interest rates have been moved away from the account vs current HBD staked. That should tell the difference... (note: We could go a different direction, where we see printed HBD from interest as Hive rewards too, and that could affect the HP KE I mentioned above... negatively, because effectively that's what the interest is doing... but that has room for debate among many... so hence why I defaulted to HBD KE 😎😉).

So effectively, HBD KE from an account would be...

HBD KE = all time HBD Interest claimed / current staked HBD

This is obviously my interpretation... Maybe there is a better way to stay mathematically correct and still show what we want to see when someone interacts with us.