I have no idea if USB WiFi dongle will use more CPU power than wired ethernet adapter (depends on many factors).
USB ports already have some linux drivers (for example, mouse), so why not add more drivers to a system?
This will not dedicate some USB port for WiFi, it will just add more flexibility for all ports.
Not everyone uses scope as stable not-movable device attached to concrete wall with anchors

For example, you have to move oscilloscope within your lab to different places and want to save screenshots to SMB share.
With WiFi support, you can just find a wall socket with 230v inside, not triyng to find ethernet or attaching wifi router to scope

I think, possibility to use WiFi USB dongle will just add flexibility not removing any existing features.