Does HA need to be on the same subnet as "works with HomeKit" devices in order for HomeKit Controller integration to find them?

I get the “Aborted: No unpaired devices could be found” message when trying to add the HomeKit Controller integration. But I have several devices that are HomeKit-compatible, such as a Rachio sprinkler controller, WeMo devices, and Lutron Caseta switches.

I assume that, being a Local Push integration, the problem is that my IoT devices are generally on a VLAN/subnet which is distinct from the subnet that HA runs on. So far this has not been a problem, but does this imply that I need to move HA onto the IoT subnet?