The c-machines console is hard-coded to always scale the local view of the remote desktop, and at the same time to always resize the remote desktop itself on the server. (Resizing on the server is like changing the resolution of your monitor.)

Local scaling is problematic since it reduces image quality (https://github.com/cockpit-project/cockpit-machines/issues/1390)

Remote desktop resizing is problematic because our console is pretty small by default and the remote side might have trouble with small resolutions, or changing it around whenever the browser window is resized is just not helpful. (XXX jira issue here).

The noVNC viewer app has a three-state setting for this: "nothing", "local scaling", "remote resizing". I think the idea is that both local scaling and remote resizing at the same time does not make sense. If remote resizing is declined by the server, the user will notice and can then select between "nothing" and "local scaling" as preferred.