Mike, I would say the use of the planishing hammer should include exercised caution. In the recent Model A door skin job we did...
https://www.allmetalshaping.com/showthread.php?t=19947
…..we originally only intended to fabricate the one skin shown in the first picture. Scott had recently purchased one of the reproduction X-181 planishing hammers and had removed the inner bracing of the other door to planish out those dings/dents, and thought he was done with it. The PH did a fairly good job of smoothing things out but his approach was a bit overzealous in that you could feel a ridge around the entire perimeter of the "repaired" area. Basically he had stretched a plateau that pushed out from where the skin should have been. That's primarily why we went ahead and made two matching skins.
So just like sandblasting, the size of the hammer (media size) and the velocity of the swing (air pressure) can rear their ugly head and make more work for you. Each job may have a different measured response.