It really depends on the horses.
Like someone else said previously, sometimes an older horse who has been-there, done-that can suddenly become herdbound when accompanying a young horse.
I could take my old mare absolutely anywhere; she was a fantastic traveler and would settle in immediately at any venue. I took her and a young horse to a show together, and guess which one lost their mind the moment I took one horse out? I’m not sure if it’s some sort of protective instinct or what, but my very experienced mare lost her mind repeatedly.