An Aaron Wan-Bissaka cross flicked Tyler Adams’ arm, with no one appealing for a spot kick live.
But referee Chris Kavanagh was asked to pause as VAR looked at it, deeming that there was contact and Adams’ arm was not in a natural position, sending the ref to the monitor.
The penalty was awarded and Lucas Paqueta gave the Hammers the lead with just three minutes to play.
Thankfully, Enes Unal struck a sensational free kick three minutes later to secure the Cherries a point.
Iraola said that this exact situation was discussed before the season with referees, with managers assured that it would not be punished.
Speaking to the media after the game, Iraola said: “I'm very disappointed with the penalty.
“Very, very disappointed with the penalty. Because it's an action that we spoke before the season started with the referees.
“They give expressly the instruction not to tell our players to defend with the hands behind the back, because it was not natural and they didn't want football to become something like defenders, like with the hands behind their backs.
“I said, okay, we give this instruction because it's costing us penalties and [they said] no, don't worry, it's natural, it's not going to cost you.
“First one, penalty.
“It’s obviously natural because everyone that has played football, you go running to defend, to block, a shot, a cross, whatever you finish with one hand down, one up is like this always. It doesn't matter, right, left, it's always like this. It doesn't change a lot.
“Also the trajectory, they almost scored the goal with the header from Fullkrug, I think, and I'm very disappointed.”
(Image: Richard Crease) He said there was some confusion when the VAR check was going on as to what they were actually looking for, as the benches searched for if Illia Zabarnyi had transgressed in the moments after the cross.
He said: “But it's not that nobody noticed, it's that you’ve expressly told us that the defenders cannot defend with their hands at the back because we don't want the game like this.
“Okay, then what happen next week? What will I tell the defenders?”
The Basque boss said the referee who spoke with them before the season about this ‘will remember the conversation perfectly’.
“I'm sure he's now remembering the conversation because I asked specially, I told him we do this because it's costing us penalties,” Iraola said.
“Because if there is a handball here you are punishing us.
“That's why we say to the defenders, okay, you have to defend with the hands at the back. ‘No, no, don't worry. That is not going to, if it is natural.’”
Iraola also said he had spoken with Howard Webb in depth before the season, with the PGMOL chief explaining well the referee’s side.
He added: “But now it doesn't matter. The arguments and the discussions is finished. It cost us two points, I think today, that’s it.”