Re: Is this even legal in the EU?
There are ways to prevent the update from happening. So your argument is specious: what you bought was a system that would receive updates to improve the user experience. This is just an improvement, because a phone exploding in your pocket is an experience that can be improved by the mechanism described. If you prefer having your nads scorched, then you can take steps to avoid the update.
The key point here is not that the device is being disabled because it's unfashionable, but because it's dangerous and people expect Samsung to make good damage caused by the thing exploding. So Samsung is *obligated* to make the thing safe, even if that means disabling certain functionality (like, e.g., it working), otherwise Samsung is complicit in the damage caused.