Defiantly NOT true.
This is rumor is probably related to Intel’s attempt to create a very secure system back in the 90’s based on the internal thermal sensor.
The NSA used its influence to fabricate a story so the project was abandoned and we ended up with AES which given enough time, the NSA can break.
I worked for the Intel processor design team for 20 years.
I remember back when Intel wanted to put unique serial #s on each 80486 processor that could be identified outside the box, that privacy advocates cried foul.
Since then, that seems like nothing.
So then, the Intel CPU is vulnerable to NSA snoping?