I introduced the regression, it's not Godot's fault. This makes me look very dumb, because I am
EsotericSoftware/spine-runtimesfb11c02

I've just fixed it and am building new binaries. Wait for this build to finish:
EsotericSoftware/spine-runtimesactions/runs/6907742739

Then fetch the new binaries from
https://esotericsoftware.com/spine-godot