That sounds like the kind of tactic i would come up with!
Me too.
A nearby alarm would always go off when they were away & it got quite annoying.
They got the alarm installer to come & check it so each time he went out & looked up at the external sounder I set our alarm which makes our external sounder beep.
He must have thought there was a fault that he couldn't resolve & it ended up with him disconnecting their alarm.