There was quite a gap between the home and away fans in the Kippax, with iirc two sets of (laser blue) steel barriers which curved towards each set of supporters at the top, and a no mans land of a couple of metres in between, but like you, I absolutely don’t recall any netting between the two sets of supports - and I always used to enter the Kippax terrace through the left hand tunnel and my memory is still (just) pretty exceptional. Not infallible for sure, but I’d be very surprised if I was wrong.
Edit: just checked the footage of the 5-1 and can’t see any signs of any netting. If it wasn’t up for that game, then it’s hard to imagine it being up for any other, and it’s also difficult to imagine it being up episodically. That tunnel was right next to the away fans too.