This feature has been added since GSX for MSFS came out, and it's there because is the only way to automatically operate doors on the PMDG, and send away its own vehicles that would otherwise conflict with GSX ones, since they can't be removed in any other way.
Most user appreciated this feature so I couldn't imagine why anybody would turn it off, considering it purposely uses the secondary FMC precisely so it won't disturb you while operating the main one ( unless you always play as F/O ), but we might consider adding some option to turn if off in a future update.