During uncoupling, after the fifth wheel is unlocked, the AAMVA procedure says to pull the tractor forward only until it is clear of the trailer, stopping with the tractor frame still underneath it. Why?

AAMVA CDL Manual, Section 6.4.2, Step 7, p. 6-9

Landing gear can bend, collapse, or sink into soft asphalt under a loaded trailer's weight. By pausing with the tractor frame still positioned under the trailer, the driver keeps a built-in backstop in place, preventing a dropped trailer and possible injury or cargo damage if the gear fails at the moment of separation.