Originally Posted by SBMC
"Think about it - he is intentionally stepping off the cliff;"
Yep.
Originally Posted by SBMC
"that is not the same as "jumping down" which requires a move action (you can read this entire 4 page thread to see the arguments of that made)."
Absolutely.
Originally Posted by SBMC
"The PC is trying to avoid the move action by "stepping off" the ledge."
What move action?
Originally Posted by SBMC
"Then, you are saying he hits the ground (and gets the same tumble check as anyone who did "Jump Down" per the RAW)"
No. I'm saying he gets the same Tumble check - against DC 15 - to reduce falling damage that anyone who falls gets - including people who trigger pit traps, who are bull-rushed off of ledges, whose featherfall spells expire,
and those who jump down from a height.
Anyone who is falling can make a Tumble check to reduce the distance fallen - for purposes of damage - by 10', once per jump, as a
"free reaction."
It doesn't matter what causes you to fall, just that you do, in fact, fall.
What he doesn't get is the Jump check - against DC 15 - to reduce the damage calculation by another 10', because that requires a move action.
EDIT:
A series of examples, freshly edited

:
Bob the Warrior (+6 Jump, N/A Tumble) jumps down off of a 20' cliff. It costs him a move action. He fails his Jump check, takes 1d6 points of normal damage, takes 1d6 points of nonlethal damage, and falls prone.
Bob the Warrior (+6 Jump, N/A Tumble) jumps down off of a 20' cliff. It costs him a move action. He makes his Jump check, treats the fall as 10' shorter, and takes 1d6 points of nonlethal damage.
Bob the Warrior (+6 Jump, N/A Tumble) is bull-rushed off off of a 20' cliff. He can do nothing to ameliorate his fall, takes 2d6 points of damage, and falls prone.
Bob the Warrior (+6 Jump, N/A Tumble) willingly falls off of a 20' cliff. He can do nothing to ameliorate his fall, takes 2d6 points of damage, and falls prone.
Phil the Rogue (+6 Jump, +6 Tumble) jumps down off of a 20' cliff. It costs him a move action. He fails his Jump check and his Tumble check, takes 1d6 points of normal damage, takes 1d6 points of nonlethal damage, and falls prone.
Phil the Rogue (+6 Jump, +6 Tumble) jumps down off of a 20' cliff. It costs him a move action. He makes his Jump check but fails his Tumble check, treats the fall as 10' shorter, and takes 1d6 points of nonlethal damage.
Phil the Rogue (+6 Jump, +6 Tumble) jumps down off of a 20' cliff. It costs him a move action. He fails his Jump check but makes his Tumble check, treats the fall as 10' shorter, takes 1d6 points of nonlethal damage, and falls prone.
Phil the Rogue (+6 Jump, +6 Tumble) jumps down off of a 20' cliff. It costs him a move action. He makes his Jump check and his Tumble check, treats the fall as 10' shorter, and takes 1d6 points of nonlethal damage. (EDIT: As noted below, Jump and Tumble do not synergize in the way I thought they did.)
Phil the Rogue (+6 Jump, +6 Tumble) is bull-rushed off off of a 20' cliff. He can attempt a Tumble check to ameliorate his fall. If he fails, he takes 2d6 points of damage, and falls prone. If he succeeds, he takes 1d6 points of damage, and falls prone.
Phil the Rogue (+6 Jump, +6 Tumble) willingly falls off of a 20' cliff. He can attempt a Tumble check to ameliorate his fall. If he fails, he takes 2d6 points of damage, and falls prone. If he succeeds, he takes 1d6 points of damage, and falls prone.