pfSense

On the Interface Groups Edit page, Group Name field, it says "No numbers or spaces are allowed. Only characters: a-zA-Z."

But the actual validation allows:
a-zA-Z0-9-_

and there is a check for "Group name cannot end with digit."

What is the real requirement?

Either update the text under the Group Name field, make the validation match what the text says, or some combination.

It looks like the validation was updated in 2.3.3 and 2.4 branches, but the text not changed.