Since any evidence of strenuous effort renders it impossible
to convey an impression of ease and lightness, it follows that the
hand must, first of all, be emancipated - that is to say, it must
be quite freed from the hampering weight of the arm. ''The
hand must be light as a feather" repeated Deppe often. But
how shall it be rendered light? The hand will be light only
when it is carried, instead of carrying itself, over the keyboard.
The lightness and freedom thus imparted to the hand is effected
through the agency of the shoulder and arm muscles, which sup-
port and carry the hand...
While there is arguably some wisdom behind that, it suffers from the simplistic polarisation that the weight might merely be "on" or "off" and fails to take into account the far greater complexity of reality. There are a wealth of different ways of distributing balance between hand and shoulder. While many indeed burden their hands (typically with muscular pressures of the arm that are wrongly perceived as being caused by gravitational "weight") there are also many who strive to withhold so dogmatically that their shoulders and elbows become rigid. The hand frequently becomes completely disconnected from the arm due to fixation.
Functional balance is a lot more complex than supporting weight either at the hand alone or at the shoulder alone and we should be thankful that more modern writers have begun to go beyond the simplistic idea that it's a case of choosing between shoulder and hand. Some people are in a position that is better served by seeking release whereas others are better served by looking to withold more. However, when you realise that you don't have to make a choice between two (impossibly exaggerated) dogmatic extremes, it's far easier to find something workable.
Seeing as you advocate the finger that relaxes after sounding the note, I should be especially interested to know what keeps a key depressed- if the arm is 100% supported at the shoulder end and the finger is supposedly going to cease its activity after the notes sounds. So it's neither weight nor ongoing finger activity? What remains to stop the spring lifting the note back up, precisely? There's really very little point in dealing in historical sources, if you do not stop to consider their practical ramifications.