I noticed a strange skill interaction while trying to make a build for a Primal witch. The Treat Wounds skill action specifies that the DC and amount healed by the skill check can be increased based on your proficiency with Medicine:
"If you’re an expert in Medicine, you can instead attempt a DC 20 check to increase the Hit Points regained by 10; if you’re a master of Medicine, you can instead attempt a DC 30 check to increase the Hit Points regained by 30; and if you’re legendary, you can instead attempt a DC 40 check to increase the Hit Points regained by 50. The damage dealt on a critical failure remains the same."
However, the Natural Medicine skill feat lets you "use Nature instead of Medicine to Treat Wounds." The use case of this is clear for a basic Treat Wounds action, but less clear for the alternative DCs. Would you replace all instances of "Medicine" with "Nature" for the purposes of attempting a higher DC, or would the character need to also have the requisite proficiency in Medicine in order to raise the Treat Wounds DC?