I'm with you there, it's the same in Cresciano, and this euro cave with Dave Graham problems. If the guide doesn't make it clear where the problems start then you should write another one or inform visitors in good time, if you want people to get the most out of your local crag, and personally I feel quite strongly so I'd say you have a responsibility to do this (inform people) where possible. Otherwise you lose your right to come back and say `ooh that sarts 3cm lower'.
Of course this is only an issue with contrived, eliminate, or non natural problems and routes ;-).
Even then, I know people might be bothered about not doing the route themselves, but the grade is the point - the kid himself probably felt like he'd just climbed 9a.