How do sticky triggers & waits work with multiple devices?

I am trying to get a sticky trigger to work when multiple devices are selected for a given attribute (any) and I am failing to see the behaviour I expect. What I'm seeing is that a first event from device A will start the "stays" timer. Another event from a different device B coming in during the stays timer effectively resets that timer. If device B fails to stay, the trigger fails.

I am seeing this behaviour in both Basic Rule and Rule Machine. I am also seeing a similar behaviour with Wait for Events actions (Simple Automations gives a slightly different result for some reason, only the timer resets, not the trigger).

Is this the expected behaviour? The documentation is not explicit about this scenario.