It would seem a little "enthusiastic" to be fair, when you consider
you had live open busbars on the LV board :-}
More reason to sleeve, as they could touch the bars.

LOL they could touch any phase or neutral more easily by going
straight for the busbars - and if it's a standard 500kVA sub, many
transformers are connected to the ACB via uninsulated overhead bars.

If they're already in the sub, they're at more risk from the other
exposed extraneous metalwork, than by having to take a screwdriver to
a socket to put themselves at risk.

That's completely ignoring the possibility of them playing with the HV
side of things !