1.) You must have just orbed. I don't know why, but it doesn't work if you change your player's position directly.
This is because you are teleported to a position 2.156 units lower than the camera's position upon using /dropPlayerAtCamera. Subtract this value from your 147.86 value (and other values I am about to mention) and you will find that it still works.
2.) You must fall exactly 147.86 Torque units. So if you're falling onto a 2x2 brick, you have to fall from a height of 148.46 TU.
Okay this is maybe a bad explanation but here goes:
When falling, your velocity always increases at a predictable rate.
These1 are the first 128 velocities (Z, negative, absolute) you will find your Blockhead going through. As you might guess, a physics engine updates position by taking the velocity and subtracing a value based on how much time has elapsed since it was last processed.
These2 are the first approximate 128 positions (Z, negative, relative) you will find your Blockhead at. Should your current position be within ~0.016 units of the ground, there seems to be some code that nudges your position slightly (like 0.00033 units?) that occurs and breaks flow in the physics routine before the next velocity frame position update, which would kill you.
So if you fall from within 0.016 (still unsure about range) of the heights in 2nd link, you'll live.
EDIT: Changed the second link a bunch of times; added "approximate" disclaimer but they all should work.