I think that the 500fpm descent has its origin in the hold - as soon as an aircraft reports leaving a level another can be cleared to that level - try that with TCAS
Slightly off thread: It would be "nice to know" if a flight is affected by the mach restriction, AD, placed on some 737s after deicing restricting them to not above 260IAS. To put it mildly , "The best laid plans of mice and men fu' aftimes gang aglae." when someone in a sequence suddenly reduces
also the almost unique (in the UAS) characteristic of the 145 of "changing up a gear" on reaching cruising level and increasing speed by about 50 knots.
433 Fingers rapped, not on our team; it was meant to be a thick ear, but you put your hand up
"Climb as if your life depended on it, because it does." = oops, I f****d up!