Like the previous generation, it has the same problem with power supply, namely that it only works on 5 V via USB. It is nice that it is universal, but it means that it is necessary to make a 230 V socket, put an adapter in it and then a cable for power supply. For real use by the client, it is useless. It is unsightly, a socket with an adapter is a big deal. It would be nice if the sensor was rechargeable or battery-powered. Alternatively, it had a different type of connector, for example, RJ54 for power supply via a UTP cable or one that is easy for the client to manufacture. The cameras also suffer from the same problem. Especially the outdoor version. To extend the large USB connector, you have to make a 22 mm hole and have a socket somewhere behind the wall nearby. I know that this is mainly solved by software, but I still think it is a channel through which suggestions can reach the Sonoff company.
I am agree with you 100% that presence sensor with usb 5v power supply is useless for client. 
That’s why my current usage of sonoff presence sensor only as far as experiment in my own bathrooms. 
But battery solution (rechargeable or not) also may not fully solve the issue with client:
- client need to change / recharge the battery by themself, if they know how to do it;
- when client change / recharge the battery, the position and angle of the sensor will differ and make the automation may not work.
Some issues that I found during my experiments using sonoff presence sensor (currently mine is SNZB-06P):
- it sometime stuck not reporting presence or away, so I pair it with smart socket to schedule reboot daily;
- not only for fix the stuck but also fix the zigbee stickiness
- when the sensor powered on, it not immediately reporting presence or not (checked with debug mode);
- in setup phase, I change the position and the angle of the sensor a lot in order the automation works exactly the way I want it to; sometimes need days to check to make it right;
- I can not change the position of the sensor drastically because of the cable and usb adapter fixed location and also the position of usb type c in the sensor body;
- in bathroom condition, you need to worry about moisture, humidity, and using usb type c without proper protection will make the sensor quickly become rusty; even though mine not yet shown any rust, but I am very worry about it;
- cable dangling for the sensor is not getting wife approval (let alone client’s)
With above points, change it for UTP RJ45 POE power also arise other issues:
- the sensor is very small compared to cctv camera, connecting it to UTP cable make adjustment to sensor position and angle difficult
- still need to think about moisture and humidity, which make the sensor can not be small anymore
- cable is still shown - dangling
- you can plan where to put the utp cable, but when the sensor unable to work in that location, you screwed
Then what ? I don’t know yet. 
Some pictures to make it real and share the pain of it.. 
Above picture show 2 sonoff sensor: the one that is closer is motion sensor (battery powered), the other one is presence sensor with usb cable dangling. Both connected using magnet to the ceiling, so I can move the position a little bit more freely.
Above picture shown: in order to setup the sensor, I have to create a manhole in the bathroom ceiling..
Above picture shown: presence sensor not only connected to the usb adapter, but also smart socket in order I can power cycle it.
Above picture is zigbee map at ewelink cube. The smart socket also helps with the signal. In my ideal, the motion sensor also need to go to presence sensor or socket instead directly to coordinator.
The overall design is somewhat unfortunate, the relatively long narrow body is suitable for corner applications but for mounting on the ceiling itself it is impractical and ugly, installation in false ceilings is complicated and if you place it vertically downwards it sticks out from the ceiling. I personally use other sensors that are only about 3 cm high and battery operated. I bought the presence sensor only as a test, it cannot be practically applied to a client. 1. larger base smaller height. 2 power supply if it has to be, it has to be on the base and not in the moving body of the sensor (just bump the cable and the setting is gone. 3. different type of connector