Another reason right to repair is so damn important. If all of a device's memory were thoroughly documented, then this type of attack would require hardware modification, making it more expensive and easier to detect. And if hardware revisions were documented, the community could do things like document visual changes to circuit boards for automated visual comparison. Whereas with the current state of hostile code like ME/PSP, I can imagine a (larger) backdoor being created merely as a side effect of a "search".