It exists, although it’s not called direct association, and it depends on the zigbee profile being used.
You’ve all seen it in the ZLL ( zigbee light link) profile such as with the Philips Hue dimmer switch and a hue bulb. No coordinator required.
https://www.amazon.com/Philips-Hue-Installation-Free-Exclusive-Assistant/dp/B016AEHU70
And if you’ve ever read the community FAQ on why the hue bridge is a bridge, not a hub, it references it as well.
Just as one example, if you add an IKEA handheld remote to your network and then join it to an IKEA bulb, you could then take your smartthings hub off of power and The remote will still control the bulb. Same end result as zwave direct association, but for a different set of device classes.
@professordave
ZLL controllers cannot generally be The targets, so you can’t really do it with two switches. You could have two switches each of which control the same smart bulbs if they’re all ZLL. Like two Hue dimmer switches and some hue bulbs.
So it’s a little different than zwave direct Association in terms of. The device classes that can be targets, but you can definitely set up a virtual three-way, but only with a zll light as the shared target.
https://www.reddit.com/r/Hue/comments/5ef2pc/can_i_assign_multiple_dimmer_switches_to_one_bulb/