Yeah I don't know what the problem is for the "flip flop" it's pretty evident that as the system is now that they cannot just go through with this and everybody be happy. Which is what they promised each other and what's most important. So that's why The Emperor is going to be a "tyrant" just to change the laws and Paul is going to take care of her side as well.The Emperor by saying he is going to become a tyrant is that he will increase his power to crush the power of the nobility totally so he can change the law without resistance. This is so he can marry Pauliana and allow her to keep her knight hood, territory and freedoms.
In the past IRL when emperors or kings tried to change succession law/law on noble privileges there would usually be civil wars, succession wars or uprisings if the sovereign didn't have the necessary influence to force these changes through.
Of course that's just my idea of what's going on.
It never made sense for Paul to spend her days sitting on a chair playing the wife. She chose what she values more.Personally, I loved this chapter, they felt so in-character and I wouldn't wish for anything less for them.