Another way to look into the whole scene.
Virat felt uncomfortable to disclose the truth about why Pakhi stayed back. He knows that Pakhi stayed back because she has feelings for him, but he cannot tell that to everyone. He is also embarrassed with the thought that she stayed back the whole night with him and also with what the doctor said (calling Pakhi his wife).
When Omi had said that Sai sent Pakhi back, he was shocked, then Sai asked Pakhi if she asked her to leave, Virat kept looking at Pakhi in disbelief. Sai kept prompting her to reply and he noticed that Pakhi refused to answer her. Virat also heard Sai's word "Banavati aason se jo jhoothi kahani likhi hai jise padkar ghar ke saare log mujhe galat samajh rahe hain, uska jawaab toh aapko dena hi hoga".
Virat I guess had made up his mind to clear Sai's name from all the accusations in front of his family members after what Sai spoke.
Sonali then jumped in saying Pakhi never lies, Virat immediately defended Sai that Sai also never lies.
Sai then added that whatever Pakhi would have said you would have all blindly believed it.
"Aansoonon se lipta hua jhooth aksar sach lagtha hai, hota nahi hai"
I believe Virat could see the truth in Sai's words, he kept looking at Pakhi. He would have realised how true Sai was, that Pakhi would have manipulated his family members against Sai by showing some fake tears.
He could see everyone were targeting Sai and asking her questions, accusing her of insulting Pakhi and the way Karishma spoke was the last straw.
The topic had changed into truth and lies, so he would have thought he he can as well tell what he actually had told Pakhi in the hospital, because that can anyway be shared with the family.
The truth is that he did anyway ask Pakhi to leave and take rest. So since all were targeting as if Sai was lying, he might have thought, he can tell the truth since Pakhi can't deny that he said that. He knows that Pakhi anyway won't be able to admit the real reason behind staying back and so will have to accept what he was claiming.
At the end he had anyway cornered Pakhi by asking if he had said that or not. That wasn't his intention but I believe he had this time decided to play it smart (by ensuring he tells one part of the truth which cannot be even denied by Pakhi) with Pakhi.