There was a time when 1K companions officially got the 1K allowance, although I never observed it actually granted. As of the most recent baggage policy update, it is 2x50 lbs for all companions on the same record.
Note that confirmed upgrades to business or first (even one segment in that direction) now raise the weight limit to 70 lbs for those passengers. So if you can get upgraded, you'll have 5 x 70 lbs.
I can say that not all UA baggage agents know these rules.