So... I read the article and I still don't know what, exactly, is the T2 chip or what, exactly, makes it different from other ARM / Intel hybrids, other than several different ways of expressing "it's incredibly, totally great" and "Intel is untrustworthy, so let's trust Apple instead" and "this changes everything all over again".
(It doesn't, unless you arbitrarily consider small, incremental changes exclusive to Apple products as the opposite of small and incremental just because of the size of Apple.)
It’s a chip which replaces the controllers (previously several of them, from different vendors, that Apple didn’t have control over) for disk and network I/O, speakers, microphone, camera, cooling system, etc. with a single Apple-designed chip. This lets Apple add features to their hardware unsupported by other controllers, move some features from the CPU to this new chip which can reduce attack surface area and free up CPU cycles for something else, save space on the motherboard, and maybe save money.
(It doesn't, unless you arbitrarily consider small, incremental changes exclusive to Apple products as the opposite of small and incremental just because of the size of Apple.)