Normally this (gear down) is not required, however:
If you have for instance an "older" 737 NG (-600/-700) wing aircraft, one which has subsequently been retrofitted with winglets but did not have a pre-modified wing to facilitate these, speed brake travel was reduced significantly after wing reinforcements were installed for winglet installation. This then reduced the effectiveness of the speed brake (in an emergency descent). Combined with a lower weight it could then be impossible to reach 10,000' in the specified certification time to reach it.
Thus, a BBJ-1 flown years ago had it IMPOSED that at the onset of the emergency descent the gear MUST be selected down as one of the first memory items (as soon as extension was within limits prior to initiating descent). A simulator exercise enforced this policy for the operator's crews.
It may have been invariably required for similar aircraft (-600/-700, with an older unmodified wing, thus requiring wing reinforcements, restricted speed brake travel as a result and retrofitted winglets) when operating at low weights.