I see your point in that the amount of the fees are not part of the calculation of the penalty.
However, why would anyone mine a block for which they will not be paid?
The incentive would remain to move fees off chain, especially as the coinbase reward decreased.
Off-chain fees would not be subject to the seizure and redistribution of the rollover.
Better for the miner to guarantee positive revenue and get it on the side.
I still don't follow you.
Why does it matter wether the fee is payed on- or off-chain. The penalty is the same and the miner has to pay it either way.
By miner has to pay it, we mean "not paid to miner but to rollover pool instead"? They miner is never paying anything, they are simply not given the reward, yes?