RC failsafe on Stabilize or Arcro modes

Hello folks,

While I tested the RC failsafe on SITL, I noticed that there is difference between document and actual behavior of ArduPilot.
Based on the document (https://ardupilot.org/copter/docs/radio-failsafe.html), “if the copter is armed in Stabilize or Acro modes, and the throttle input is at minimum, the copter will immediately disarm.” However, when I simulated low throttle (below throttle failsafe level), flight mode of ArduPilot was changed to RTL as shown below

.

On the other hand, when I input “rc 3 1000” --> “rc 3 900”, it finally triggered disarming as shown below.

Could you help me to figure out which behavior is correct for the RC failsafe? Thanks.