It means the linesman didn't know, in which case it was up to the ref to make a decision, with the aid of the in-goal official if he saw it clearly, which as you say he probably didn't. Benefit of the doubt to the attacking team.

You don't often see it but a horizontal wave of the flag is one option the touch judge has when adjudicating on a goal kick - up for a goal, down for a miss, horizontal for a don't know. If one touch judge makes a decision and the other is a don't know, the referee can overrule the one who made the decision. If both touch judges agree the referee has to accept their decision.

Granted not the horizontal flag waving but I'm sure this season we've had it twice in the same game where the 2 touch judge's made differing desicions for a goal kick and the ref gave one and dismissed the other.

I remember being rather upset about one of them, lol.

cas away by any chance ?

No it was at the Willows.

oh yeah that one too
did banish that one from the memory banks til now

i was thinking of the one at cas where the ball hit the OUTSIDE of the post deflected in the opposite direction to the posts only for the touch goons to look at each other and think....What the hey lets just give it

Thanks for that. I'll try to remember it.