When I was doing my early rank boards of review back in 89, they were really hard. I was tested thoroughly, but that was the expectation given to me, that I would be able to answer any question and / or demonstrate any skill that I had learned to get the requirement signed off. I studied my scout book all week before the BoR, to be sure I knew everything I was supposed to have learned while working on skill awards and the first aid merit badge. It was actually kind of scary, but that's just how it was done in my tiny troop. Of course, I never forgot how to tie most of my knots, or my first aid skills, so, there is that.
My star rank BoR was the most scary, knowing everything about all 5 merit badges I earned ... but that is when things changed, I wasn't so much tested on the specific skills, but rather, it was a conversation about what I had learned. Even in 89 & 90, this probably wasn't the way it was supposed to be done. But I think my SM, hey, he was the troop adult, so he did the BoR with his wife, the CC, and that was it, I think his goal was to make sure we would always be first class scouts, as long as we should live, and know what a first class scout should know.
Would I do that today, no, but only because it is against the rules, not because it wouldn't be the right thing to do.