Thanks for your response!
Here's the situation on my side: on the initial render, <AppEmbed /> only takes up about a quarter of the browser window height. The only reliable way I found to stretch its height to fill all the available space was by using a fixed height via frameParams.
That’s why I tried setting fullHeight={true}, hoping it would help dynamically calculate the proper height.
However, after further debugging, I realized that the unpredictable height behavior is actually caused by the parent containers wrapping <AppEmbed />.
So I think this issue is no longer relevant and can be closed. Thanks again!