Ach
I repeat my previous advice which is to get the Executive Committee to talk to a strata lawyer (at their expense).
Meanwhile, send them a letter telling them that you have been advised that this is not your responsibility but (if you wish) you will consider letting them move the air-con unit at their expense.
It actually is clear-cut, according to the advice I have had on other issues. So a polite letter telling them they’ve got their facts wrong is quite in order.
They wouldn’t be the first EC or strata manager to fall foul of this . Logic and commonsense would suggest they are right but those two characters aren’t around too often in strata matters.
And don’t get bogged down in nitpicking about written complaints. The law seems to be on your side and that gives you a position of strength from which to negotiate and reach a happy compromise.