The switch shortcut form (/user/N/shortcuts) displays the 'id' field when the associated text field 'label' is not visible.
I first saw this in a 9.5 installation, confirmed in 10.x.dev on simplytest.me.
On a default Drupal installation:
Currently, you see a set of radio buttons for the existing shortcut sets, and a text field named "Machine-readable name".
The 'id' machine name field is showing when the associated text field 'label' is not because in the SwitchShortcutSet form, 'label' has a #states condition that it is only visible when the 'set' field has the value "new", but 'id' does not. Adding the 'visible' condition to the 'id' field keeps it from appearing to users without permission to create a new shortcut set. For users who do have permission, the form seems to behave normally.
Needs work
10.1 ✨
The change is currently missing an automated test that fails when run with the original code, and succeeds when the bug has been fixed.
It's such a small change, and has been like this for so long apparently, I feel like I must be missing something.
Thanks for reporting, next step would be to add a test showing the issue.