He doesn't know that he's in heat the officer never told him. That was the officer speaking to himself after leaving him. So he honestly thought he was just hurt.
But he did know the other guard told him that the inmate is in a rut
"I forgot to mention that Alejandro is in his rut as well. Well, Mr. Taeseo is also an alpha, so it should be alright."
- the prison guard says this to himself after Mr. Taeseo leaves the room
He didn't say it to him he said it to himself that he forgot to tell him.
Oh sorry maybe I wasn’t focusing well
He knows but take this risk, he should have given an alfa that duty for today. If he is gonna be pissed that happened he is passing me off too