Uncle Al
Scavenger
Think the change was around January of this year.Last I checked, sometime during early A20, this was not the case; the zeds that get up as you trigger an attack volume, would keep running to the player, even if the player moved. Until the player was properly seen by the zed, "re-stealthing" was impossible.
A dev mentioned planning a change to have that "chase time" be shortened, but I haven't followed up to check if something was changed. It sounded like only the timing was going to change, such that the zeds would still run to the player for the timer duration at least.
If you're saying it has changed since then, then how does it work now? The zeds just sprint to the trigger location? Which patch have you tested this on so I can check?
There's a long discussion thread, including @Boidster 's extensive testing, which I've linked to below. The change to volumes happens during the course of the thread.