Gc.com UK reviewers aren't in any way bound by GAGB's guidelines - they're required to work to gc.com's guidelines. There seems to be some confusion over this in the Groundspeak forums on occasion.
But there is a degree of flexibility, and as Lac says, they do take account of local issues. Also, there are situations where a landowner agreement requires that caches placed on their land must meet GAGB guidelines. If one of them doesn't, then technically at least, it doesn't have landowner permission. I know our reviewers take matters like that into consideration too.
Do not go gentle into that good night.
Rage, rage against the dying of the light. (Dylan Thomas)