It's very clear now.
After hearing Leela bhabi's pran. Obviously, BBB producers are very well known for producing suspense as they did yesterday. It's the same thing now. Birju was seen in a way to make people think that he hates Baby. But if you think about it, that's not so. If he had been then he must have spoken at least a word. But, instead he got angry that baby didn't have faith in him and couldn't tell a small fact.
One more thing, why was Baa this much angry? and that also that she went to Birju to scold him! Well if you think ahead of the script it's clear that producers wanted some reason for Baa to go to Birju but return with him as a groom.
Birju was not upset that Baby has polio, he was upset that Baby didn't have the faith in him and didn't tell him about this small thing polio. So he was very angry and went back only to come back with baaraat to prove that He love's baby.
You will see this tomorrow. Ba will enter KrishnaVilla with Birju in a wedding baaraat.
It was never thought by anyone that Baby will be married off before Dimple. But there you go. In a way it's good Baby is elder so should get married earlier.