It is new to Pixel. Unfortunately only a few (mostly expensive) phones have display support on the USB C port. For example the more expensive Samsung phones have it.
I used to use this feature a lot on my Samsung S5. Was super handy to just carry the adapter cable in my suitcase when staying at a hotel. Easy way to watch streams in my hotel room. Almost any TV in hotels has a free HDMI port to connect to.

And now they just have to force manufacturers to either at least security patch devices for, let’s say 10 years, or force them to open source everything the community needs to continue supporting this device. It never happened to me that the battery died before support ended.
Just had that issue with my Pixel 3a XL. No more security updates. Had to replace it with a Pixel 6a but I liked the 3a XL more. It there was any community support for the 3a XL, I would rather sell my 6a again.
Ah. Didn’t know that. But they really limited functionality. I’ll give this a try to see if that’s all I need. Will continue to support my Add-on otherwise.