Variation In Distance Between 5RM and 1RM.

[stef]

Since (as highlighted by yourself and monsieur Courtland above) to improve 1RM strength, one must practice 1RM lifts, and that 1RM best indicates the ability to move the most force (s-t-r-e-n-g-t-h), then it must follow that to get stronger, in the surest definition of the term, we ought to be practising those max singles from time to time?

That was not my point. My point is that there are differences between people with good genetics and those without. Someone with 1RM far from 5RM is different from one with 1RM close to 5RM. A bigger spread comes from training, but can't turn a donkey into a thoroughbred.

1RMs are a performance measure and not terribly important for training. Please keep in mind that singles != 1RMs. Training is almost entirely not about RMs at all, PRs in a rep range sure, but not actual rep maxes. People commonly mixup the two and they're actually quite different events.