This is one of those things where the people who know assume it’s obvious to the people who don’t, even when it isn’t!
Leviton made zwave switches, but added “enhanced” communication which did “instant updates” between the device and the controller. This was their Vizia RF+ line. You’ll notice all the switches in this line have LEDs which are intended to display the status of the scenes controlled by those buttons.
Lutron has multiple patents regarding two way communication between a light switch and a controller. Starting around 2005 they began suing lighting device manufacturers, including Leviton and Control4 for having infringed on these patents.
Ultimately everything was settled pretty much in Lutron’s favor. Leviton and
Cooper agreed to pay license fees to Lutron, so their controllers still have this update feature. However, this also made their switches more expensive.
So Leviton introduced a new, less expensive line, the DZ line, which did only plain vanilla zwave processing. No “instant status” update, but also no license fee.
These devices are considered “incompatible” with the Vizia RF+ controllers because the instant status can’t be updated.
If you install the devices with a third party zwave certified controller, like ST, you can still use plain vanilla zwave with either, so you can use them in the same installation. You just can’t utilize the instant status feature for Vizia RF+ devices unless both secondary controller and controlled device both have the patent controlled feature.
All of the above is easily verifiable.
I think it may also be true that the Vizia RF + devices should only be included in a 3 way or 4 way setup with other Vizia RF+ devices, but I’m not 100% sure on that one.
Anyway, hope that helps.
edited to add Lutron-patent devices, regardless of manufacturer (Cooper, Leviton, Lutron, whoever) use instant status update for one hop only! Intended for a local controller in line of sight to the device.