They can have it, as ARM TrustZone. This is an independent ARM chip and is in fact used in the AMD PSP. I don't know if some or all of these laptop SoCs would have one, though. Some (most?) Android phones have one (see: https://googleprojectzero.blogspot.com/2017/07/trust-issues-...)
ARM TrustZone isn’t a chip at all, and it’s not a thing that an SoC could have. It’s just another operating mode of an ARM processor. It’s more analogous to x86’s SMM than to PSP or ME. TrustZone is also fully documented AFAIK.
So the real question is: will the laptops let end users replace the TrustZone kernel?
There's a lot of SoC specific stuff moving over into the Arm Trusted Firmware that sits below the TZ kernel. The upstream ATF is BSD licensed, so while some chips have open source implementations, others might only exist as blobs.
It's possible to build out SoCs that require a closed-source blob that runs on one of the ARM cores, doing basically all the same jobs a PSP or ME does.
