The point is not whether Ehsan’s feelings are true love or just infactuation. The point is the usually thoughtful sensitive Viaan’s lack of considerateness.
There is a first time for everything and hence there is the small chance Ehsan may have fallen in love - Viaan should consider that. Secondly - Viaan himself has changed so why does he not consider that his friend may have changed too.
This part of Viaan’s behaviour is totally at variance with the rest of his characterisation.
Actually this is not about whether Ehsan's feelings are genuine at all. It is about Katha's choice.
Ehsan has basically just declared that he wants Katha and will get her by any means, by eliminating anyone that comes in his way. In response to this, Viaan has tried to explain to Ehsan that he doesn't know much about Katha but that hardly seems to matter to Ehsan as he steamrolls his way towards what he wants.
Viaan's consideration has shown in the way he backed off when Ehsan wanted to take Katha to Rajasthan. He left it open to Katha to decide what she wants to do and Katha herself came forward and chose the Lonavla project and the Rajasthan project aka time with Ehsan went to the side.....lol so Viaan's consideration hasn't gone anywhere, he is respecting Katha's choice above everything else right now. And he's not a mindreader that he should sit and imagine how genuine Ehsan's feelings are when Katha herself is not showing any indication of wanting to go to Ehsan.....lol