The important question is ... how far away was the drone?
RTH is one of the most important features to understand well.
There are several pages about it in the manual.
This is part of the information on page 18:
a. If the aircraft is further than 20 m from the Home Point when the RTH procedure begins, it ascends to the pre-set RTH altitude and then flies to the Home Point at a speed of 12 m/s. If the current altitude is higher than the RTH altitude, the aircraft flies to the Home Point at the current altitude. Forward and Backward vision systems are enabled.
b. If the aircraft is between 5 m and 20 m from the Home Point when the RTH procedure begins:
i. If the RTH at Current Altitude option is enabled the aircraft flies to the Home Point at the current altitude, unless the current altitude is less than 2 m, in which case the aircraft ascends to 2 m and then flies to the Home Point at a speed of 3 m/s.
ii. If the RTH at Current Altitude option is disabled, the aircraft lands immediately.
c. If the aircraft is less than 5 m from the Home Point when the RTH procedure begins, it lands immediately.