Heck, if I'd had someone taxiing in front of me at 5mph, I would have tried to overtake them on the first bend.
Now that the GPS will tell us our ground speed, surely, there must be a reasonable maximum speed for a given type. Get behind a slower type, and despite one's enthusiasm, that would be the new datum.
And as for the phone. Try offering to taxi for a skipper going back to the pan while pouring then drinking a double double scotch, and being told to keep yer hands off the tiller when he veered to the edge. CRM? Dodging the captain's fist was CRM in those days. And that was one of the London airports and a shiny new jet. A mere phone call seems fairly innocuous apart from the attitude of the man doing it in the first place.