That's a rather low estimate. 18 AWG wire is 20.95 mΩ/m according to wikipedia. 24 AWG is much more likely, at 84.22 mΩ/m, and cheap cables that still meet USB spec use 28 AWG (212.9 mΩ/m).

The four-foot-long cable features a single USB-C port on one end that splits into a pair of USB-C ports on the other, each with a foot of cable that can be shortened as needed to keep things neat ...