For things like PDUs having the large “overall traffic” graph on the overview page for the device is fairly useless. It would be much better to display a graph of the voltage the device is getting, current output, or load in watts.
You can submit pull requests to change this for the devices you have in question. The file to edit is includes/definitions/OSNAME.yaml
That’s only for the small graphs at the top right and when hovering over the device name though? html/pages/device/overview.inc.php has require 'overview/ports.inc.php'; (the Overall Traffic box) unconditionally.