I wouldnt say poor habitat means there should be none, just means that they do not populate in large numbers. I might be wrong.
I don't think you are wrong.
To be truthful I haven't a clue, it's all just guesses.
Of all the species of deer when it comes to fecundity Roe should spread the fastest really, they can have 2 sometimes (rarley) 3 kids every 12 months so why they aren't in great numbers in the Midlands with strong populations North and South is a mystery.
Maybe the Yam Yams are just really efficient Roe killers?