Pick Clean +3?

Skill description: Reduces the chance of obtaining HQ items to 0% but increases item yield by one or two. Number determined by your perception rating. Does not increase item yield if all gathering node items start at 0%.

I've seen some +3, as in the item will have no number next to it to signify one per gather but will show a four after the skill is used. The nodes don't have a gathering yield increase either.

What's the trigger?

Best guess at this point is simple RNG resulting in some sort of skill "crit". I've only personally seen it happen twice but then I don't gather huge amounts each week and I don't track how frequently I use Pick Clean. Perhaps others have been collecting data on what they've seen.

I think this happened to me on nodes that had an hq rate buff, as if that messed with the perception influence on yield.

Seems to be RNG and can happen on any node regardless of level, but will only proc on materials you're already at +2 yield for.

For the sake of data collection (though I still think it's reliant on RNG) I just had +3 from Pick Clean on a +2 Gathering Attempt node.

Edit: about an hour and a half later I just had it happen a second time on a node that had no modifiers. Just chalk it up to lucky RNG.