Re: On the plus side...
The snap had been shot by my wife on her smartphone (Ugh) so it was in 3:2 format (re-ugh). I took care to re-frame it properly and change it to the proper 4:3 format for photographs, only to have the millenial shopkeeper tell me that she'd have to crop it as it was not in a standard format.
"Proper photographs" - that is, on 35mm film - are 3:2 (https://en.m.wikipedia.org/wiki/135_film). Hence 6x4 (inch) prints.