Pleased to have stimulated debate!
I think I would accept that JP combos are
less related than some owner combos. But I wouldn't accept that they're completely unrelated, as I find it very hard to picture a scenario where e.g. Inthepocket, Fact To File, Iroko and Corbetts Cross all run in the Turners whilst he has no representatives in either the Arkle or Brown Advisory. He might be less in the habit of splitting his runners, influenced by sheer weight of numbers, but I think there's still an element of it. I have no statistical analysis to support this 'conclusion'.
I also accept that some of the value is extinguished by covering multiple combinations of runners. But, since plenty of us do this with runners from different stables/ owners for the same race in various different doubles and other multiples as part of our antepost strategy, I don't think we'd be extinguishing value to any greater extent by covering multiple combinations of single owner runners vs multiple combination of single stable runners or in fact multiple combinations of any horse for the same combination of races.
And so I feel that there remains an element of value in the approach.