What is the question exactly? Why did the sauce come out okay? Were you expecting something different? What is ‘curdling’ as opposed to creamy?
As others have said, cooking flour, fat and milk is going to make the base for a creamy sauce (bechamel). The picture looks very thick. I may add a bit more milk to get it more creamy and less gluey. Some acid would also improve the taste, maybe a splash of vinegar.
In my experience, if you make gravy in the same pan after making fried chicken, it’s going to come out delicious, because chicken grease = delicious. So as long as you’re frying chicken, then adding flour and milk to what’s left in the pan and cooking it, it’s going to taste good.