Will bear “Full House” in mind as I already qualify for it. ::o)
And yes, there are some odd difficulty/terrain scores around . . . I do sometimes wonder whether there’s an element of “That was the hardest thing I’ve ever done, so it must be T5” going on, or whether people are thinking “People might get hurt trying, I’d better up the T rating as a warning”.
Trouble is, if you do that, you end up running out of space at the top of the scale for caches that are harder still to get to (eg need climbing kit, a boat or both).
And that’s just for terrain, which is (imho) far easier than difficulty to get right-ish.
(As regards challenge caches prompting over-inflated terrain scores, my experience in trying to complete the grid was that it wasn’t the T5’s in themselves that were the problem, more the just plain rare DT combinations. )
Don’t think I’ve done Take Moor Care 2, so can’t comment.