Allow opposing directional input setting is not being saved

[raziel711]

System info:
OS: Windows 11 Pro 24H2 26100.4351
RetroArch version: 1.21.0 stable
mGBA core version: 0.11-dev c9bbf28
GPU: NVIDIA RTX A500 Laptop GPU
Driver: NVIDIA RTX Driver Release 570 version 573.42

I have an issue with the "allow opposing directional input" setting not being disabled when the core loads, even if it appears that way in the quick menu screen:

Even though the setting appears disabled, I am able to cause glitches that result from when the left and right buttons are held at the same time. If I toggle the setting on and off, then it is disabled and there is no longer any issue; however, the setting is not saved between sessions. The next time I load the mGBA core, I have to manually toggle it on and off again to disable it.

Log:
retroarch.log

mGBA opt:
mGBA.txt

I was looking through the log and there is no GET_VARIABLE being set for mgba_allow_opposing_directions. Is that by design or is there some other way to save the mgba_allow_opposing_directions setting?