It can be a simple case of deal wali shaadi. He might have told Pakhi not to expect anything from him. We are doing this shaadi only for Vinu. But there is no bandhan on you. If at anytime you don't want to be in this marriage, you can break it.
He laid out the same terms & conditions to Sai - and in the initial days, used to show all his love & friendship to pyaari cheez without hesitation - because he had clearly told Sai everything before hand.
So he may be nonchalant about the complexity of the new revelation in his life (Sai)& his complex marriage...because from his POV, his terms & conditions to Pakhi were clear....and to Sai - he has been faithful.🙄 Sai & Pakhi's emotions be damned...