So I used a skillpoint to upgrade the hand brush tool for Antiquities Excavation. This increased the "max intuition" from 2 to 4.
Based on the tooltip, I thought it would allow me to bank extra intuition. That way I would not lose intuition (have it wasted) if I wanted to brush off some extra dirt - and still have the generated intuition saved so I could use the shovel or trowel (which cost 2 intuition). It would make it easier to find bonus loot since I can dig up more dirt.
However, there seems to be a bug. On PC, using the shovel or trowel (cost: 2 intuition) when I have 4 intuition banked because of my upgraded skill causes the shovel/trowel to fire twice, using up all my intuition. Even if I only pressed the tool key once and just want to use the tool once.
This is bad, because now I can accidentally overdig by having the trowel dig twice - damaging and destroying the antiquity! The upgrade makes the skill totally worse. This is really sad, because I now have to respec to undo the upgrade - costing me more gold then I ever earned from antiquities.