@IshRash 

This mount guide is actually first presented in the setup process, and there is also a backup on the device setting page. This guide aims to offer precise installation recommendations, helping the doorbell perform at its best in a wide range of user environments and scenarios.

Regarding the installation guidance you have questions about: 

• If the porch is shallow and the doorbell is positioned directly facing the entrance, the doorbell can easily detect the activities outside the porch. If that's a busy street, the doorbell will be woken up frequently and detect more unnecessary events, draining the battery quickly. In this case, installing the doorbell on the side of the entrance (and using the wedge) can help to limit the doorbell’s field of view to focus on your porch area while minimizing interference from external activity.
• On the other hand, if the porch is deeper, the doorbell is less likely to be triggered by distant movements.

There isn't a strict rule about whether the doorbell should be installed on the door or the wall. The placement mainly depends on the typical path people take when approaching your entrance. 

It seems your doorbell will run by battery instead of being hardwired, so I'll also explain this part here.  For a battery-powered camera/doorbell, it remains in sleep mode most of the time to preserve battery life. To wake up the camera, it relies on a PIR sensor, which detects changes in infrared radiation and is primarily used to detect objects with heat signatures, such as humans, animals, or moving vehicles.

When the camera is installed directly facing the monitoring area, it may fail to detect activity when someone walks straight toward it. This happens because the heat signature generated by radial movement - walking directly toward the camera - produces minimal changes, which the PIR sensor struggles to detect. As a result, the camera may not wake up and capture movements effectively in this scenario. You can check here to learn more: How to Install and Configure Battery-Powered Cameras for Optimal Detection Performance