I agree that using a gutter is a nicer way to do things. That said, this was once a practice so common that older, round meter pans often has threaded hubs on the side, for feeding the other meter.
Here in Reno, the practice of differing rates for heating water are long gone, and the second meter is removed when a service change is done.
Indeed, this work may be the result of a non-professional doing a DIY or non-permitted service change, replacing the fuses with breakers. Or, considering housing prices, it may be the result of converting a basement, etc., into an apartment.
