I would say tax evasion is more serious than fibbing to an insurance company. I don't fancy HMRC knocking on my door.
Most modern cars have the ability to see numerous parameters in an app. Certainly on my last 2 cars this has included total mileage. This indicates that the car is sending this information to 'the cloud' before it arrives on my phone. It wouldn't bother me to give permission for mileage info to be shared with HMRC and billed automatically.
There's no standardised system for this though, so I can't see HMRC being able to negotiate with every car maker to have it send, securely, mileage data, VIN details and whatever else. Plus there are a number of cars that don't have the cellular connection, including a number of cars that only had 2G and 3G support. Now 3G is switched off, many won't even be able to send data reliably on GPRS or EDGE standards. Some cars can be upgraded, many cannot - and this includes EVs that aren't even that old (less than five years in the case of many Stellantis vehicles).
Also, I think a lot of people have no real fear of HMRC and will see this is a bit of a game and there being no harm done if they lie about how much they've driven.
It's quite possible to make all cars made after a certain time have the means to send the necessary data, and to disallow the future registration of vehicles that don't, but then you have a system that only applies from this day on - and no way to manage older vehicles. Of course with EVs still (relatively speaking) in their infancy, that might potentially work.
You could also force all other EVs to have hardware fitted, but I think the Government knew this wouldn't fly and that's why they're opting for a half-assed idea.