Why it is here

One conditional,
well placed.

A menu that animates shut is ordinary. A menu that notices it is about to change the page underneath, and declines to animate for that one case, is a decision somebody had to make twice: once to build the transition, and once to admit it was wrong in a specific situation. Everything else here — the delayed visibility flip, the caret, the trigger that reads back its own selection — is competent standard work. The conditional is the record.

The whole record turns on one conditional: the panel animates shut when nothing changes, and is cut instantly when the selection does. Motion that knows when to get out of the way is rarer than motion that is well timed.