That makes sense... most tractors have what looks to be superfluous holes & brackets that are only used during assembly.
However, these holes & brackets come in handy when adding 'personal' modifications. I have an open-station, 'bare-bones' tractor (4105) that doesn't come with a rear/side view mirror. The factory mounting holes on my 300CX FEL 'pillar' turned out to be the best place to mount a van-style side view, after knocking up a mounting plate.