Semenyo launched the ball into the Gunners box after 67 minutes, Huijsen guiding the ball into the far corner past David Raya to equalise at the Emirates.
But after the game, Iraola said they had tried to encourage Semenyo to use his long throws more this season, and he confirmed to the Daily Echo that they’ve known the Ghanaian has the ability all season.
“It's something that we do always in pre-seasons,” he said.
“We try to see how long they arrive and then we put them in a line, do it in pre-season.
“And we know ours are James Hill and Antoine Semenyo, the two that arrive longer. But it's true, the one the other day was especially good, the throw in.
“I think also comparing to our stadium, he has more room, more steps to take. So I think it's maybe a little bit easier here is more difficult because maybe you have to do it with two steps.
“So it's a little bit more difficult. But it's something that definitely we encourage him to do.
“Sometimes Antoine doesn't see it, but when we've conceded this season, against Brentford, against Ipswich and it's very uncomfortable when you have to defend these plays because it's not even winning the first contact.
“It's normally the second ball is quite close around the box and it's sometimes a matter of luck, a matter of where the ball is, smelling the danger. I think it's something that you if have, you can use it.
“Depends on the game state, but I think it's a good addition to have.”
Despite knowing about Semenyo’s skill with a throw in, the Cherries were surprised with the distance and trajectory he managed to get on the ball.
“Probably the one the other day was longer than we expected,” Iraola said.
“It was not lobbed, it was quite firm.
“Normally in these plays it's difficult to score in the first contact. You need just the first touch and someone else to get a second.
“But the delivery was so good that Dean could finish it straight away.”