I used the tool when agreeing a contract with the Royal College of Art. It decided (quite correctly, given the unambiguous conditions) that I could operate as self-employed. But the RCA insist on running it as 'casual labour' anyway, presumably because the extra cost to both of us of doing that isn't worth the potential hassle if HMRC fail to keep their promise of 'standing by the results'.
HMRC needs to be held to account for their ineptitude and FUD. No wonder nobody trusts the government.