Apparently the USB driver stack doesn't report the cable's eMarker chip data back to the OS. However benchmarking actual transfer throughput is the ultimate test for data connections (vs charging use cases). Unfortunately, TFA doesn't really go into this aspect of cable testing as the tester seems to only report eMarker data, which pins are connected and copper resistance.

Since a >$1,000 automated lab cable throughput tester is overkill, my thumbnail test for high-speed USB-C data cables is to run a disk speed benchmark to a very fast, well-characterized external NVMe enclosure with a known-fast NVMe drive. I know what the throughput should be based on prior tests with an $80 active 1M Thunderbolt cable made for high-end USB-C docks and confirmed by online benchmark reviews from credible sources.

There would be too many factors involved for a proper test. Many laptop USB controllers would probably not even have the capacity to run two ports at full speed simultaneously.