Hello @Ajinkya Aher Below is the response from the Microsoft product team, I hope this helps with your initial query.
The sample app simply renders the result of the detected planes directly from Unity’s ARFoundation (specifically ARPlaneManager, which is powered by ARKit or ARCore depending on the platform). We do not control or manipulate that data; we simply render it for the user and use it in our code for detecting collisions. The behavior that is described in this forum question is expected, as ARPlaneManager detects and renders multiple planes. If we only wants to see/interact with a single floor plane, we will need to do extra work to interact with the ARPlaneManager and the detected planes.