Total Warfare auto-fails PSRs if the result is 'automatic'. It's one thing I remembered well when combing through it to see what changes were made from the BMR.
I double-checked my old BattleTech Manual, and the rules under falling damage to a pilot don't state to add any modifiers other than 1 for each level fallen. There's no mention of the Mech having fallen only one level if it only falls inside its hex and drops its own height. And the BattleMech Manual is a direct compilation of BattleTech, CityTech, and AeroTech.
Reviewing the old rules reveals some interesting points for interpretation.
For instanceActuator damage for physical attacks only talks about modifiers for 'damaged actuators' and doesn't mention anything about missing actuators. That comes later. Which means the idea of treating missing actuators as damaged is not an initial concept for the game. So, a Locust, even though it is missing the lower arm and hand actuators, should be able to through full damage punches with its chicken wings (Elbow to the face) as well as a Wasp with a full arm. But, the Wasp has the issue of taking lower arm damage, weakening its punches. This makes sense when you think about a an armored chicken wing being like a solid box. Whereas a damaged forearm kinda flops around or isn't putting up near as much resistance when used as an add-hoc club as a full strength undamaged arm.
'Clearing woods didn't put out fires in those woods' would be another example.
And, thus, when rolling to see if a pilot takes falling damage, one could infer that there should be a general +1 or +2 modifier to that roll when a Mech goes down simply because the pilot is falling 2 or 1 levels, making for something of a 50/50 chance to dash your brains against the dashboard.