Though far from perfect, the 1954 definition as a rule-of-thumb has worked for me for coming up to 40 years as a collector and researcher, and as a listener, 20 years longer than that as a guide to knowing which tins to open (no longer the case, sadly).
It is in much need of updating and improving with all the information that has been gleaned over the last half century plus, but as the only alternative on offer appears to be the abandoning of all definitions - tearing all the labels off all the tins - the original will probably see out my remaining days comfortably.
Suggesting '54' is a 'rule' is little more than tilting at self-constructed straw men; it never was, nor was it intended to be; a rule-of-thumb, no more.
As the fat geezer with the cigar once said about capitalism, "by no means perfect, but it'll do till something better comes along."
Jim Carroll