I’ve said it before- it is very possible but highly unlikely that this method would be used.
Manufacturing a microchip that works AS IT IS SUPPOSED TO but also does malicious stuff (in hardware) is extremely expensive and unlikely to reach a large enough audience to make it cost effective, when there are considerably easier ways to hack a computer.
Ok for the pedantic here, the government has enough money to make one, and could put one in the hand of a country they wanted to spy on, but the same rule applies- it would be easier to do it in software than in hardware.
Unless finding it in the hardware gave those looking a false sense of security and made them less likely to look harder in the software.
Or vice versa.