I don't know that I can agree with that, maybe if the enclosure were something other then NEMA 1 rating - then you have something to go on with breaking the rating of the enclosure, but NEMA 1 enclosures can have all kinds of holes in them that don't get sealed or used in some way.
Keyhole shaped openings are a good example even for a hole that does get used for some function - do you see inspectors requiring sealing the remaining opening in such a hole?
In looking at the picture, I believed the holes were drilled by the installer and thought 110.12 might apply.
110.12
(A) Unused Openings. Unused openings, other than those
intended for the operation of equipment, those intended for
mounting purposes, or those permitted as part of the design
for listed equipment, shall be closed
to afford protection
substantially equivalent to the wall of the equipment.
Where metallic plugs or plates are used with nonmetallic
enclosures, they shall be recessed at least 6 mm ( 1 ? 4 in.)
from the outer surface of the enclosure.