Why Actor-isolated property cannot be passed 'inout' to 'async' function call?

Considering below dummy codes:

@MainActor var globalNumber = 0

@MainActor
func increase(_ number: inout Int) async {
    // some async code excluded
    number += 1
}

class Dummy: @unchecked Sendable {
    @MainActor var number: Int {
       get { globalNumber }
       set { globalNumber = newValue }
    }

    @MainActor
    func change() async {
       await increase(&number) //Actor-isolated property 'number' cannot be passed 'inout' to 'async' function call
    }
}

I'm not really trying to make an increasing function like that, this is just an example to make everything happen. As for why number is a computed property, this is to trigger the actor-isolated condition (otherwise, if the property is stored and is a value type, this condition will not be triggered).

Under these conditions, in function change(), I got the error: Actor-isolated property 'number' cannot be passed 'inout' to 'async' function call.

My question is: Why Actor-isolated property cannot be passed 'inout' to 'async' function call? What is the purpose of this design? If this were allowed, what problems might it cause?