Dave, you are no doubt right, but in this case both glasses are clearly marked Pint
I once had a ruler thingy that measured the head on a pint, and costed it to pennies shortchanged by the pub, probably more of a Southern problem where little or nil head is expected, hence the Pompey CAMRA
I do think Trading Standards is a bit OTT though, unless bar person was trained at the Basil Fawlty pub persona school