Why? Obviously the original / main client accepted the blocks that had the lower fee otherwise the blockchain the people using his version of the client would have forked away from the mainline blockchain.

Since it didn't obviously the old client accepted it.

The sooner we get it back to the correct value the better so we don't persist the error since we evidently do not need to cause it to persist.

(Especially if it is possible that one of these days it might end up creating a block that the original client, still in use probably for a long time to come by people who use what worked instead of trying out new versions to discover what new bugs have been introduced, might not accept. It seems like you are potentially trying to possibly blow away all the serious users who are conservative about sticking with what they know works instead of risking all on some new release. If it is not a deliberate hard-fork, fix it before it becomes one. The goal here is not to produce a hard-fork release, is it? If it is, then a block number far in the future should be chosen as the block at which it will come into effect.)

-MarkM-