Unfortunately, the headline is somewhat optimistic compared to the reality, I think.
The thread makes it sound like it could have been disabled due to errata or performance issues. Basically, it looks like the software Google is shipping intentionally doesn't use MTE on the Pixel 11 hardware. That raises the question of...what does Google know is wrong with MTE on the Pixel 11?
I've read that there's a significant performance cost to MTE on Android (or on Tensor). It might just be that.
Nothing is wrong. They just don't use MTE yet, they probably have other priorities. They wanted to save some costs until they will use MTE, so they removed some hardware acceleration and downgraded the GPU. Simple as that.