My test:

sealed class MyException : Exception() {
    sealed class SubException : MyException() {
        class SubSubException : SubException()
    }
}

inline fun <reified T : Throwable> baz() {
    try {
        throw MyException.SubException.SubSubException()
    } catch (t: Throwable) {
        when (t) {
            is T -> {
                println("my exception thrown!")
            }
            else -> {
                println("don't recognize it!")
            }
        }
    }
}

This prints

my exception thrown!

as I'd expect

🤦 Shit. Ignore me.