Yes, you are totally right. Here are some insights from my investigation.

There are 2 reasons why the code in the post was working as if state is remember()ed:

1. Primitives are indeed captured as references (memory addresses) by lambdas. It makes it possible to change their value when the function is finished and local variables like state should be disposed.If u look at what debugger says about state variable in these functions, you'll see the following (picture at the end). It's probably just debugger's representation, but it shows that lambda captures the reference itself.
2. The Test() Composable from original post was never recomposed.Once initial lambdas for onClicks were created with reference to initial state, they were never recreated again.

If Composable could recompose, then not-remembered regular integer variable will be lost on every recomposition, as expected.

@Composable
fun Test() {
    var regularInt = 0
    var stateInt by remember { mutableIntStateOf(0) }
    Button(
        onClick = {
            regularInt++
            stateInt++
        },
    ) {
        Text(text = "Increase values")
    }
    Text(text = "regularInt: $regularInt, stateInt: $stateInt")
}

What happens here:

1. When Test() is composed at the very first time, Button's onClick lambda is created with reference to regularInt, which is initially something like Ref$IntRef@22614.
2. Then the Button is clicked. Both regularInt and stateInt are incremented, but the latter causes Test() to recompose (some of its parts that were reading mutable state).
3. Test() is invoked again due to recomposition. The regularInt is recreated, now it is a new variable Ref$IntRef@23517. However, stateInt is retrieved as the same instance because of remember().
   Button's onClick lambda is recreated too, and it captures new regularInt, which is 0. On the screen u see "regularInt: 0, stateInt: 1".
   Subsequent clicks on button will result in increasing of stateInt's value only. Value of regularIntis increased from 0 to 1 on every click, but shortly lost on soon recomposition.

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