It's a ground-up or down argument. It's only bad if your helper is ground-up and you're ground-down, in the same room.
Been there. Except my helper was an industrial electrician and I was a 12-year-old. Thye result: mixed ground patterns, but I wired faster, so thee were moRe ups. I could see thyat happening with data.
Btw, all of my cat5 is ty-rapped mixed with phone, romex, se, speaker, and just about every other type of cable known to man with no problems.
I could see thyat happening with data.
