This clip shows that it was probably real rope though the point and strength of attachment is not clear...
I would have thought that even if the connection was only strong enough to ensure the rope does not fall off unintentionally, it could still lead to circumstances requiring at the very least, an undesired need of a change of underwear. Or what of the rope separating at a critical moment and being drawn into an adjacent prop!?
Not withstanding that they were brave men in those flying machines in those days back then...
Flying Display At Hawkinge - British Pathé