Answering my own question for those who suffer from the same problem
The SBUS protocol has a “failsafe” flag. If you’re using SBUS to communicate to FC, no matter what setting you make on your receiver, Ardupilot will “hold” all channels and do what’s set up on the FS_THR_ENABLE option.
If you set it to disabled, you’re going to have a flyaway, as the FC will hold last commands until your battery drains