I’m no expert on Victorian law, but if the strata manager says the committee alone can’t make decisions about common property, then the strata manager certainly can’t, regardless of any delegated powers they may hold.
The strata manager’s boss must know they have screwed up and is now basically ass-covering. It’s time to tell them who’s boss. Get your secretary to rewrite the motion the way you want it and instruct the strata manager to send it out, unedited.
Remember, the owners are in charge – not the strata manager! If the strata manager doesn’t like that, they can take their business elswhere and wait for the bills for fixing this to come in.