Every chip design created also has a large number of test vectors created with it. If the test team has done their job well then those will include random fuzz

Every chip design created also has a large number of test vectors created with it. If the test team has done their job well then those will include random fuzzing and power monitoring like you mention. As I read this article I thought about this as well. Every chip is tested as part of the manufacturing process, but as Bunnie points out, to be really secure you can't just trust the manufacturer when they say the tests all passed. If there were some way to run all the tests on the finished silicon product myself, would I trust it? It's very hard (expensive, time consuming) to test everything in a modern chip, however, it would certainly make it harder for a malicious mask change to go unnoticed.