Could be wrong but I think you're possibly judging Field mostly based on him defending at stand off against Cats at Magic when he was coming back from injury and he really struggled.
His one on one defence at full back has always been pretty decent and off the top of my head I can't think of any games he's been bad in when he's played there.

hes class as 1 on 1 last man

Well he did stop and dislodge the ball 1 on 1 against Hurrell 5 mtrs from the our line in last years CC semi,won us the game that stop.

Correction 1 mtr from the line

Can’t quote the Reaper for some reason but he’s definitely missed how good Field has been defensively at FB. Maybe his game at 6 against Catalans is in his mind. At FB Field is fantastic defensively. Obviously his pace makes him pretty impossible to beat from deep but he’s very rarely beaten one on one, even on breaks closer to our line. It’s always surprised me how good he is on that side of his game.

You are going to wait a long time for an answer.