Adding different widgets to an activity (the default one for example) and then removing said activity only removes the widgets (visually) from the desktop but doesn't stop them from running. I created the activity in the Workspace KCM and deleted it through the Activities manager in Plasma then check in the widgets explorer whether those widgets were still in use. Reproducible: Always Steps to Reproduce: 1. Add widgets to an Activity 2. Remove said Activity 3. Open the widgets explorer sidebar and check the running widgets Actual Results: Activity and widgets are removed from the desktop but they're still running. Expected Results: Deleting an Activity should remove and stop the widgets.
Good news: They're not still running (scientific method; I added a plasmoid that runs a command every 2 minutes + added gdb breakpoint. It was triggering whilst activtiy was active, then that stopped when activity stopped) The widget explorer does still list them though, which I think is incorrect.
*** This bug has been marked as a duplicate of bug 341154 ***