Will OS check if such python lib is installed or script running in the background? Then those that doing ad fraud will move to programmable board as BLE keyboard/mouse/hid. Even microbit can can be programmed as BLE HID device [1]. Add external camera on unattested device that will stare at attested device screen and you can automate lots of thing. Sure this is more complicated to pull off but will probably eventually happen anyway if this is a lucrative business.
In the end WEI wouldn't prevent ad fraud / fakes but would end up used for restricting other things.
Most computers come with a trusted platform module which increasingly runs more and more services related to media handling. On modern Macs the T2 chip is an A8 or A9, meaning it has the same power of a modern iPhone and handles everything from device input (mouse & keyboard), to webcam decoding to media decoding. When you watch netflix on a modern macbook, the video buffer that is displayed is actually a shared memory buffer from the T2 chip, which the main SoC can't actually see. If you take a screenshot you will see that the screen stays black, since audio and video come purely from the chip.
You could run a Browsers Renderer in there and you would never notice.