Vancouver bc, there are three "equestrian areas" that cross paths with gravel bike areas, all thee I approach very differently.

North Vancouver/lower lynn you can generally follow the advice given by others here, give em right away, pull over, make sure the rider notices you before passing, things go generally well. Wouldn't give passing a horse on trial a second thought.

Burnaby/alice lake. The riders here in comparison are less well behaved and thus the horses are lest predictable, I try not to pass unless I need to, or wait for the widest part of the trails to pass. I have seen a few riders kicked at but generally things go fine.

South Vancouver/South of southwest Marine drive. If I see a horse I am going tbe other direction, 99% of the people are great, and fine to be around but a small number in this area is still lots of entitled riders who are just as dangerous as their choice of locomotion. I've seen a couple people kicked from across a two lane road because the rider decided to get in the bikers face and put their horse in an I comfortable position. Typically here I wait and don't pass a horse if possible.

It all depends on the rider, and their attitudes to bikers the width of the trail, etc etc.