Posts like this are like a mechanic saying “There is no reason for a manufacturer to force drivers into having a catalytic converter in their own engine”

It's more along the lines of "There's no reason for manufacturers to forbid my mechanic from installing a perfectly fine catalytic converter just because said manufacturer doesn't like it"

Giving manufacturers full control over the software users run will not end well. Why should google tolerate a browser that runs an adblock extension? Currently they do so because the alternative would be losing users to alternatives but if they have all android devices under control and make deals with most of the browser devs (it's all chromium already and firefox is almost entirely financed by google) then you'll find yourself forced to watch ads. This is what they're slowly creeping towards.