I don't think that any intelligent person is going to suggest that isolation exercises should take precedence over compound movements, its just that there are many intelligent trainers out there that utilize isolation movements (e.g. Poliquin, Cosgrove, ect.).
Since other very intelligent trainers like the ones here eschew all isolation exercises, there must of been something - either experience or literature - that lead them to believe that isolation does not improve strength in coumpound movements. If it did, it would be quite foolish to not to use them.
I havn't had the requisite experience to make a judgement between the two camps. I can tell you that a few years ago when I was still using isolation, I was a good deal stronger in compound exercises than I am now, but that was do to far greater consistency on my part. So, I can't really compare my pre- and post-isolation phases to make my own decision.