That is great news. It seems to me like Sinbad is actually now trying to teach Belit some boundaries and manners. Also the way Belit reacted to his actions is great. One of my cats had to teach a young kitten I adopted boundaries and manners and that is exactly how he did it. My baby Starbuck used to put up a fuss though when Tegato first did this to her. The first time it happened she protested so much I separated them. The next time I took a step back and just supervised. I realized Tegato was not hurting Starbuck at all she was just mad because he was telling her who was the boss. This was how Starbuck learned appropriate play manners. I am glad to see Sinbad is gaining confidence and trying to take some control over their relationship.
Interesting little interaction just happened:
Sinbad moved in for a bum sniff, and Bêlit slapped at him, then challenged him. Direct stare, arched back, etc. When she approached for a direct physical challenge, he simply slammed her to the ground then sat there calmly watching her.
I read it as "I'm bigger than you, and this is MY house."
There was no hissing or anything of the sort, he just made a show of physical superiority and remained calm the whole time. Looks like he is slowly gaining the confidence to stand up for himself.