I believe they started to appear as a factory option in the early 90's. I have seen and have had several 80's vintage trucks with these installed. The earlier trucks did not appear to be completely set up for them from the factory but they do seem to install quite well. All of the ones I have seen were shorter though and did not interfere with the rear seat.
Can't really say for certain but there looks like some gray vinyl peeking out by the 3rd row seat hinge... which hints they might not be original to the vehicle. Perhaps borrowed from the 40 series?... which did have split bench seats?
On another note, anybody know what those brackets are, on top of the wheel wells?
I have the rear jump seats in my FJ73, they are great for small people (kids) but not that practical for adults. As Twatson pointed out, the ones in the ebay listing interfere with the rear bench seat. Mine don't do that at all. I have the same seat covers in my FJ73 but a tan color.