So, this is exactly the perfect example!
That bit in “Ain’t no Sunshine” is not really a repetition, it’s an absolute masterwork of subtle vocal technique. Every single time the “I know” is repeated there are subtle changes in inflection, intensity and rhythm which build to a really satisfying crescendo.
That’s the meaning of the Trevor Horn quote (and he’s talking about early sequencer productions like “Two Tribes” and “Relax” which are super repetitive) essentially something should always be evolving and changing even if one bar is seemingly very much like another.
If you just sampled the first “I know” from the Bill Withers and played it 26 times it would sound awful and boring. A better producer than I am would add some clever automation to add some drive, volume, filter, modulation, or maybe a riser, or something which would give the same effect of building.
I was puzzling over how I love Bicep so much, but if I try and reproduce their sparse repetitive style I find my own tracks boring and stuck in an 8 bar loop. Then I saw a breakdown of one of their tracks on YouTube and you realise that nothing is static all of the parts are constantly subtly evolving in ways which are very satisfying even if they are only barely perceptible. That’s where I’d like to be.