Ok, so as I understand it with this ruling not only we use Facing After Fall Table to determine damage direction, but we also ignore notes on results 2,3,11,12 of the Basements Table, which tell us to use 'Mech Punch Location Table or 'Mech Kick Location table, just use regular 'Mech Location Table for everything. This would result in a little fewer 'Mech sudden deaths due to falls on their heads after rolling 11 or 12 in the Basements Table, as there would be no threat of rolling multiple sixes in the 'Mech Punch Location Table, and thus loosing a head when resolving the damage afterwards.
For ProtoMechs note, that unlike Vehicles they don't have such thing as damage direction (Special ProtoMech Hit Location Table on p. 185 TW, which applies to ProtoMech falls has only one column, and ProtoMechs don't have separate rear armor facings), so my logic for Vehicles does not apply here. Personally with ProtoMechs usually being build in a configuration closer to bipedal 'Mechs, then Vehicles, I would expect them to determine facing after a fall randomly, like 'Mechs do. I just mentioned ProtoMechs together with Vehicles above, because they, along with regular 'Mechs are the only types of units that have a defined facing, and are likely to end up in a basement.
Theoretically Aerospace units (at least those taking up only one hex on a ground map), but I guess they don't need their rules here, because in TW if an Aerospace unit ends up in a Building it is Immobile (see Buildings on p. 82), and if it falls into a Basement at that point it is most likely functionally out of a fight (as it can not get out of there and is unlikely to be able to attack anything from that position, although I guess like an ECM mounted on an aerospace unit would still function as lo0ng as the unit has any Structural Integrity left, and the ECM is not otherwise disabled).