The Celtic defender was penalised for handball during his attempt to block Djeidi Gassama’s shot in the box at Hampden.
Referee Nick Walsh pointed to the spot, and James Tavernier converted the penalty.
However, the decision left Celtic players furious, as they questioned the call with Ralston’s arms tucked in as he fell to the ground and blocked the shot.
According to Michael Stewart, who was commentating for Premier Sports, VAR did not interfere with the call because the ball struck Ralston below the T-shirt line.
The pundit, who did not believe it should have been a penalty, expressed his opinion on the matter.
He said: “VAR is saying it hits his elbow below the t-shirt line. We can all see that.
“That doesn’t constitute a penalty. His arm is tucked in tight ot his body.
“Here is the other thing, if he is putting his arm down, then his rested arm on the ground, it is not given as a penalty.
“He has actually tucked it in and been penalised, I think it is extremely harsh.”
Stewart was equally baffled at the decision not to book Ralston for the handball once the penalty award had been confirmed.
The Celtic full-back was already on a yellow card, so would have been sent off if a yellow was given by Walsh.
Stewart said: “You can see Rangers players are clearly questioning the ref, ‘You’ve given the penalty, is it not a yellow card?’
“And I think it is a valid question. I don’t think it should be persoanlly but if you are giving it, surely it is a yellow.”