Is the order of Subject to events in the same frame guaranteed?

[KazukiKuriyama]

For example, if the following code is written to Value in the same script in the same frame, the events will be executed in the same order.
However, if written from another class as public from another script, the order does not seem to be guaranteed.

public readonly IntReactiveProperty reactiveProperty = new();
reactiveProperty
                .Subscribe(value => Debug.Log(value + " ")); 

            reactiveProperty.Value = 1;
            reactiveProperty.Value = 2;
            reactiveProperty.Value = 3;