When the network card tampers with the packets, this can be detected if the network protocols use the correct cryptographic algorithms to ensure integrity and confidentiality. Protecting against tampering on the CPU level is much harder, since this is where these algorithms are carried out.
>>majews+(OP)
If you think you're going to catch every possible NIC-level modification, does tampering on the CPU really matter if there's no way to store or exfiltrate the data without being detected?