Either the kicker plays him onside or he doesn't. The rules state that he does so he cannot be onside and offside at the same time.

"Any offside player..."

A player who is played onside is not an offside player!

Correct.

Tbf the eef was crap for both teams

Seems clear enough to me. He was deemed offside from when the kick was made until he was played back onside. During that time when he was offside he was deemed to have interfered with the receiving player by encroaching within 10 metres.

To be fair this thread isn't about the ref (Campbell) it's about the video ref Bentham...

You can excuse ref errors through the game as it's quick and so much is going on....sitting watching video replays and not knowing basic rules is inexcusable though!

How did Bentham determine that Finn was within 10 metres of the defender? No one else picked up the offside, so no referral from the ref or linesmen.

It all looked pretty marginal to me.

This.

As much as it might grate once Bentham had decided (probably just about correctly, albeit close) that Finn was in front of kicker and within 10 metres of Shaul at the point of challenge then he had to call it offside. The decision was correct.

Finn was never within 10 metres of Shaul...watch the replay when the kick goes up he is over 10 metres away...as far as I can see at no point is he offside within 10 metres...Hall goes past him and he is onside...

It is not when the kick goes up, it is when it comes down at the point of challenge and at that point he was less than 10 metres away. So as he was in front of Hall when he kicked it he is offside.

How can he be played onside by Hall as he runs past him, then be offside when Hall is jumping in the air to challenge for the ball?

Soon as Hall passes players and gets to the ball they are triggered on side, try end of.