I Googled around a bit and it seems like around 1900, a bunch of influential surgeons recommended that nobody should even consider stapes mobilization again, partly because the risk of infection, which could be fatal, was so great. So people collectively forgot about it until Rosen re-discovered it after antibiotics and safer surgery was available. But Rosen's technique seems to be different - moving the base of the stapes, rather than the small end connected to the incus bone.
Figured out that you could try an old technique that was already known to have superior results when it works before performing a newer type of operation? Seems quite a weak discovery if it's a discovery a all. Maybe the author didn't understand what was significant about his work so accidentally missed that.
According to other sources he did a bunch of research on novel ways to access the inside of the ear, so that may have played a part.
But no, it doesn't really go that deep into what make the operation unique.