Christian Romero conceded a polarising penalty as Tottenham and Arsenal played out a 2-2 draw at the Emirates Stadium in London, with the defender penalised for blocking a Ben White shot with his left hand early in the second half.
Romero had scarcely any time to get his hand out of the path of the ball as White let rip a shot in the six-yard box.
A penalty was not given initially, but referee Robert Jones awarded a spot kick after VAR directed him to the pitch-side monitor.
Arsenal took a 2-1 lead when Bukayo Saka nailed the penalty kick, before Son Heung-min slotted his second goal of the match to ensure Tottenham remained undefeated after seven games.
“I’ve got no idea about the handball rule. I really don’t,” Postecoglou said after the match.
“It just seems if it hits your hand it’s a penalty and then other times if it hits your hand, it isn’t a penalty.
“It is the one rule in the game I just don’t understand.
“Unless we start developing armless defenders I don’t know how you are supposed to block things and be in a natural position.
“It is what it is. You kind of hope these things even themselves out over the course of a year, but I don’t understand the handball rule. I think any clarity would be good.”
From six Premier League games this season, Postecoglou’s Spurs have won four matches and drawn two.
They’re placed fourth on the Premier League table, behind Manchester City, Liverpool and Brighton and Hove Albion.
In addition to their Premier League results this season, the Spurs have had a draw with Fulham in the EFL Cup.
“It’s not about being happy with the result; for me it was about the performance,” Postecoglou said after the clash with Arsenal.
“You can get a result here, a draw, and like I said before, you can walk away knowing that, ‘You know what, we escaped’, but I don’t have that feeling now.
“I think we went toe to toe with a top team and at times I thought we really asserted our dominance on the game. At times they did, but that’s what happens when you face top sides.”
Tottenham is now set to meet Liverpool at Tottenham Hotspur Stadium on Sunday morning (AEST).