Cortex-X4 spec, Cortex-A720 spec, and Cortex-A520 spec from ARM say they all support FEAT_MTE, FEAT_MTE2 ("Full Memory Tagging Extension") and FEAT_MTE3 ("MTE Asymmetric Fault Handling") and with the line "The Cortex®-<NAME> core always implements the Memory Tagging Extension (MTE) and therefore is compliant with the CHI.E protocol." Specifically it claims FEAT_MTE2 and FEAT_MTE3 is just a pin to activate ("These features are enabled by setting the BROADCASTMTE pin to 1.")
Then here is the same for C1-Premium which allegedly also has MTE with that exact CHI.E protocol line and so does C1-Pro. What is different is that "FEAT_MTE2" is said to be "Yes, configurable," but no turnkey solution like setting a bit listed. if I read this right, it would mean that MTE is optional and it's maybe because C1 is "sub-flagship" (ARM called it that) and not Cortex so MTE support isn't turnkey anymore.
Which is ironic considering Lord G once said:
"We believe that MTE will play a very important role in detecting and preventing memory safety vulnerabilities and provide a promising path towards improving software security."
Hopefully I'm just dumb and read it wrong or somehow the CPU suddenly supports MTE again through any flag because I still love Pixels even if their hardware is questionable. But Google is still selling phones with one of the highest profit margins without actually being a giant like Apple, so maybe they did not bother implement it, considering they are taking our precious RAM out of our phones and into the Gemini slop.