I thought I had tried that and didn't notice a difference with/without. I'll try again though. What I was really kind of looking for was to see when another person is on their mount. i.e. my assist bot, I'd like for him to notice when MT is suddenly on their mount and then summon their own when they see that happen. Figured the client would have to know when someone else is mounted or not in order to display their horse. Actually the client see's when a group member 'starts' to summon their mount as well (little icon by their group member name), perhaps capture that as an event?
Although thanks to your help on my bc/alias question I can just send a command to other bots to 'mountup' easily enough, so this is just a question of convenience/automation.