I bet the old guy is Su-ah's alpha dad
That's a good point but to be fair everybody was distracted and emotions were running high. The old guy was focused on Juhyeok before he got his shit rocked and Su-ah was focused on protecting his man and getting him to a safe place. They didn't really have time to be like "You smell like me are we father and son?" Cuz remember Juhyeok said something about the old guy smelling familiar. Plus old guy seems like a player so it's entirely possible he has a kid (or more) that he doesn't know about. And having him be interested in his son's omega might be the drive for character growth somehow.
I really hope that when Tae wakes up he punches Ilay right in the mouth and yells at him that he had been planning on coming back.