What that hardware requirement means is that only recent Macs can play UHD content from Netflix.  Basically 2018 or later MacBook Pro, 2018 or later MacBook Air, 2018 Mac mini, 2019 Mac Pro, iMac Pro and a 2020 iMac.

The Verge suggests the requirement could have something to do with the T2 chip's ability to process HEVC encoded videos.

But to put this in perspective, Windows 10 has supported HEVC out of the box since 2014 and even the iPhone has had it since 2016.

There are some other requirements too. In addition to having a T2-equipped Mac, you'll need macOS Big Sur, a Premium Netflix subscription, and the Safari browser -- other browsers will limit you to 720p on a Mac.