As explained above, a connector device is set by an event generated by the hub when the variable itself is set. Events are effectively put in a queue, and are processed by the hub from that queue. If you have other events happening contemporaneously there can be some delay between the setting of the variable and the setting of the device attribute as those other events are processed.
This isn't documented that I know of. But it's now been fully explained twice.
Connectors have very limited purposes, and checking the state of one immediately after setting the underlying variable value isn't one of them. So we don't see any need to document this beyond answering your question here.
