Unearthly being
Even though Arsh and Alan behave like they were eager to marry off Arna, they cared a lot about her. So it was important for them to feel assured about who she will choose to spend her whole life with.
Arsh knew about the reality. He was a practical man, just because two people love each other doesn't mean that their life was going to be an easy walk on the flower carpet.
Problems might not arise between the couple but it was important to support and stand by each other at any turn of their lives else their love for each other does nothing but push them away due to incompatibility and no zeal.
Arsh didn't know how his life was going to be with Noor, all he knew was he was going to support her. Likewise, he didn't want Arna to face a lack of support. He knew Ivan would support Arna in whatever she does, similarly, he wanted Ivan to stand by Arna even if Eva would be against them.