I don’t know, it seems to me that every command that goes through the gimbal is 2.4, because that’s where the board is that the antennas attach to. The antennas on the AC (main body) are 5.8, so just looking at where the antennas are located, it seems to indicate what controls can be made on which frequency. Ie. the RTH command must, if initiated by the device, go to the RC, which then sends the command out, not on 2.4 as received, but 5.8.
I may be wrong, but it seems like a lot of extra work to make 2 circuits for RTH, since the 5.8 is usually the strongest link.