Oh they absolutely were. Their research into the time periods in which they wrote sketches was often far better than that of "serious" films and TV series. Notably, Terry Jones has had a deep professional and personal interest in medieval literature and art his whole life. I'd bet good money on his being intimately familiar with medieval killer rabbits when they worked on Holy Grail.
They were mostly fancy lads and lasses from Oxford and Cambridge so I shan't be too surprised.
It’s got fangs! Look at the bones!!
What's he do, nibble your bum?
Would it...help to confuse it if we run away more?