Yes, I know what you mean, Niall, and for me that in part explains why I've played so few par 5s that I've ever even liked, let alone loved.
So, based on a comment Tom D made on another thread, I was raising the possibility that maybe it's actually a bit easier to *create* -- on a flat site, with lots of earth-moving -- those specific stratagems and related visibility and recovery options etc than it is *find* them -- in a minimalist sense -- on an otherwise great site.
All of which is to suggest -- very tentatively -- that if Mark F is right in his OP, this might be one reason why.
P