It kind of isn't. The EU is giving the cell companies guidelines on how they should test their batteries, and then report their numbers back to the EU. So "Apple" are testing their apple phones and then telling the EU their alleged numbers.

Standardized testing isn't the end all be all. Manufacturers have wiggle room. Most of the time you can also voluntarily derate yourself. EPA testing is standardized, but there's a surprisingly wide margin that you can test your car at.

BMW is pretty famous for derating their HP output so they're closer to whats available at the wheels. Every other manufacturer will measure at the crank (the balls)