Completely different issue. It’s based on existing business arrangements. WINK made the decision early on that they would have an official integration with Lutron. That’s why they work with the pico remotes as well. SmartThings chose not to pursue that relationship, probably in part to control the price point of the device.
Zigbee does not have the concept of secondary controllers in the same way that zwave does. So it’s not a standard integration. It’s something that wink and Lutron agreed to work out for themselves.
On the other hand, Smartthings has an official integration with harmony, which wink does not. Again, it’s not that wink is technologically inferior, but rather that two companies agreed between themselves to work out a direct integration.
It’s all part of brand differentiation. Each company decides where it wants to invest and what price point it wants to ultimately hit, and which features it thinks customers will want first. As customers we vote with our dollars as to whether they guessed right about the features that were important to us. And of course we can send them direct feedback through the forum topics like “suggest a device” to help encourage them to make future integration decisions in the directions that we would like to see.