See, reiterating what I saw today, in a different format -
Adi is very secure in his relationship with Imlie - his POV is very clear. He wants to complete this divorce & register his marriage with Imlie at the earliest, but wants to to that without hurting anyone - that is where his issue lies. He refuses to acknowledge that Malini cannot understand the meaning of the word subtlety and wants to still handle her with kid gloves.
But this does not mean that he dismisses Imlie's statement, in fact it is the exact opposite. He does not want Imlie to get involved in these tu tu main main type fights and knows that the only way to prevent Imlie from going back in to the DD jaap rabbit hole was to dismiss her worries about DD not being happy. See Adi will always have that fear that Imlie will prioritize Malini over him - he legit fainted worrying about it. Of course the situation was vastly different then, but the fact is, Adi feels that if Imlie is convinced that DD loves Adi and wants to get back with him, Imlie can very well try to patch them up. While Adi hopes that Imlie may not willingly leave, he is worried that this situation will not bode well for all 3 of them. He would prefere to ignore it rather than face it to maintain status quo and prevent Imlie from getting involved in a fight that is going to hurt her the worst. The guy is a chomu and ostrich of the first order, but he has always believed Imlie and never doubted her - that shows that MU nahi hoga, but I stand with Flower's theory - he will say something to hurt Imlie so badly that she may choose to leave Adi and go. That possibility seems the most likely to me. That will wake both him & the others to how dire the current situation is.