I asked a recently retired Electrical Engineer who was in charge of bringing all the power into our city of about 100,000.
He seems to know his stuff pretty well, and was head of the transmission unit (I used to kid him about wanting a new gear ratio for better fuel economy). Anyway, transmission of power was his thing, and he really didn't know of any published or even folk legends about the last house on the line being extra vulnerable.
His comment was: There used to be at least 9 grounds per mile on rural lines. And a ground on
either side of a pole with a transformer. I don't think it has anything to
do with being the last customer, but perhaps the quality of the grounding at
the location. Soil and moisture conditions, for instance."
Not that even older and highly experienced and trained individuals know it all, or have had the opportunity to make learned observations, but despite all the 'end of line' customers that Northern States Power (now Xcel Energy) had, none of the transmission guys felt that end of line was a danger. But, he's open to information, so IF someone has others who've noticed this phenomenon, let me know; he's not doing active research but has a very inquisitive mind.