There is a user-visible setting in the normal preferences. It's grayed out unless you have telemetry enabled.
I think the initial version they shipped PPA in had no such option because, again, the feature didn't actually do anything at the time (and I'm not sure they expanded the allow list yet either).
I then check about:config and dom.private-attribution.submission.enabled is still set to true.
Looking at the Mozilla wiki (https://wiki.mozilla.org/Privacy/Privacy_Task_Force/firefox_...) I don't see any discussion of telemetry as controlling this behaviour.
It is not clear to me what is going on or what the state of this feature actually is. Have I opted out or haven't I?
After the initial complaints they must have known it was controversial. I stand by my original point, they could have been much more upfront about this.
> I don't see any discussion of telemetry as controlling this behaviour.
As I mentioned: If the check box is greyed out, the feature is implicitly disabled, probably because you don't have telemetry enabled. The setting could be more explicit about this, which I'm sure they will refine in the future once the feature actually does anything.
You seem to be looking for a reason to be angry, but apparently Firefox picked the exact default you were looking for.
The setting being greyed out indicates that the entire functionality is disabled, and the value of the setting is irrelevant. That's a common pattern in Firefox settings when some other setting invalidates the current one. In this case, it's most likely because you have "Allow Firefox to send technical and interaction data to Mozilla" unchecked.