Arsh was indeed there because he wanted to recount to Aria what happened when he met Noor out of the blue, without any work, but still, there was reason to leave Noor clueless.
He won't usually share everything with Aria. He didn't want her to worry about him with Arna. He thought at least he could keep her happy and free from distress so that they could focus on taking care of Arna.
Looking at her excited seeing him happy, he first cleared out if she had gone ahead with her thoughts, "Mom, I neither proposed to her nor confessed. You are looking like you will throw an engagement party soon."
Aria wasn't presuming that. It was too early to think about it. Noor wasn't the type to agree with him, especially when she looks at Arsh as a senior and mentor. Aria shrugged as she leaned back on the couch and smugly responded, "If I propose to her, she will agree to me, rather than you."
Arsh: "..."