If you look at any modern desktop application, e.g. those built over GTK or QT, then they’re basically rendering stuff into a pixmap and pushing it over the wire. All of the drawing primitives made X11 efficient once upon a time are useless, obsolete junk, completely inadequate for a modern experience. Instead, X11 is pushing big fat pixmaps around and it is not efficient at all.
So I doubt it makes any difference to bandwidth except in a positive sense. I bet if you ran a Wayland desktop over RDP it would be more efficient than X11 forwarding. Not familiar with waypipe but it seems more like a proxy between a server and a client so it’s probably more dependent on the client’s use/abuse of calls to the server than RDP is when implemented by a server.
The EFF has some info about the practice - https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots.
I imagine there are ways and means of obfuscating / anonymizing the dots such as blocking the printer from emitting them (e.g. an empty yellow cartridge that the printer perceives as full), modifying the firmware, using a burner printer, or using a mono laser jet.
As a side issue, most modern bank notes have a bunch of yellow circles integrated into the design on each side. They look random but they’re in a recognisable pattern called a constellation that enables devices like copiers / scanners to recognize when people are trying to copy money or other financial instruments like checks.