Hello,
I also believe that a DHF is not a living document from my experience and just from the purpose of it. It is for the initial design and any changes that will be made shouldn’t alter the initial design. Once that happens you have a new device and proper measures should then be taken. The SOP example provided is a tricky one. If the changes in the SOP affect the design and device in a dramatic way then I think a change process needs to be don for a new device but if it is a change that result sin the same device but maybe in a quicker way or safer way then it shouldn’t matter and can be added to the DMR.