Hello HG and Lawrence, I do believe it has a bit to do with process as well as filler metal selection. In my experiences: cellulosic electrodes do need to be "worked, manipulated, oscillated, etc.", when these fillers are simply dragged along the joint there is a real chance of undercut along the toes or a lack of fill along the edges with a crowned build-up in the center of the bead. By working the eletrode in the puddle there is a much better chance of properly filling and providing the proper bead profile, IMHO.
Aluminum GMAW is another one that could be hotly contested, many folks will use gun motion to achieve the "stacked dime" look of these beads, I believe most weld engineers would not support this sort of manipulation where strength and soundness of bead are considered. Pulsing, of course, could achieve this sort of look without compromising bead soundness, IMO.
GMAW spray, on steel, stainless steel, and other similar materials can certainly be pushed/dragged with or without motion and lead to successful and acceptable bead profiles and mechanical properties IF certain criteria are met while doing the work. Too much whip, too far out of the puddle, wrong gun angles, improper machine parameters, can certainly lead to issues that would not provide for sound welds. Proving problems to someone that has certain practices ingrained into their work habit is probably the most challenging thing. They have to see it in order for it to have an impact on their willingness to make changes, I know that I am certainly that way. Well I don't know that I have made a positive contribution here, but there's my $.02. Best regards, Allan