Purpose of keyList in DAGSwap.sol

[lovesh]

Wanted to understand the purpose of keyList. Its only updated when an address is being mapped mapAddress but not being updated when an address is being unmapped removeMappedAddress. That leads to creating a larger map than required in getMappedAddresses as the length of keyList doesn't decrease when addresses are unmapped.
Is the objective with keyList to track all addresses ever mapped? If yes, then wouldn't it be efficient to have keyList be a map supplemented with 1 or 2 counters to track how many addresses were ever mapped and how many are currently mapped. That way a call to mapAddress does not have to iterate over keyList.