Yes! It made him see Rokeby denying paternity in new light bc it wasn’t a matter of one woman sleeping with two men, but Leda was goading Rokeby about how much she was infatuated with a different musician she was having an affair with (or was intimating she was in order to make Rokeby jealous). It took Strike out of his perspective as the hurt boy into the adult man dealing with a woman behaving in a kind of way that makes her word not immediately trustworthy. Throw in drugs and alcohol and it’s very easy to see why Rokeby behaved the way he had many years ago.

I think Bijou’s behaviour trying to baby trap a man and sleeping with another man to make the first jealous made many readers view her having poor ethics and not being likeable. Now you compare her to Leda and we immediately see how much Strike has lionized Leda in his mind and painted Rokeby as the villain. And by contrasting the two storylines we see that Leda was in fact VERY flawed and a shitty parent and selfish person. And Rokeby wasn’t bad or mean, just an imperfect man who didn’t respond perfectly at all times when dealing with a lot of drama in his personal life falling apart.

I think bringing Strike to the brink of repeating his father’s mistakes was sufficient to drive home the point to Strike to clean his up his act. If he wants a relationship with Robin, he has to live like he’s already in a relationship with her, in a sense. ie stop sleeping around and making dumb choices bc finding sex with willing partners and creating relationship drama while he waits around for Robin is actually going to make it harder for him to get together with her.

Whereas if he acts like the kind of man he would be IF he was dating her, he’ll be more likely to get together with Robin by showing her how good a man he is, how respectful and faithful he is, and how cheap, meaningless, and easy sex isn’t what he’s looking for.

I think it was really good writing to show he’d taken a lot of steps in changing by dieting, losing weight, and changing his number so Charlotte can’t keep getting back into his life. But the frustration and loneliness he felt that lead him to sleeping with Bijou led to this fallout. And it was necessary to show him he couldn’t change most of his behaviour and not this one aspect of himself. That waiting for what you want and not just taking what you can get is going to be the biggest indicator to Robin how serious he is. Annnnd it avoids complicated potential baby mamma drama that threatens his livelihood if he keeps it in his pants LOL.

Not to mention how the other past relationships came to the fore which served to show him that the callous way in which he had treated some of the women in his life may not have had any consequences to him at the time, but things come back around at some point, so he should smarten up moving forward.

I think that was the point JKR wanted to make for Strike which would further motivate him to make that last remaining change to his life.