True, this is because the assistant uses the pet slot. Note that if you swap zone the assistant goes away and the pet return.
This ones makes an second point, it should be possible to have the Alfiq banker or merchant as permanent pets since they are so small, they uses the senche cub model. Simply also put them under pets and here they will always be up.
It would also increase the value of them resulting in more sales.
Nopes, you can't. I'm more bothered about, that if i choose to have my kitteh banker out as companion instead of a pet, eeeevery time you re-zone, companion npc goes poof and you have to re-summon </3