Except that Rin gives Shirou prana by forming a contract with him, which only requires her to have sex once. Sakura is clearly shown to need to have sex with Shirou on a regular basis in order to dump prana into him.
Hey Mike, I know it sounds impossible, but do you know what perfectly functioning couples participate in? Sex. You know what you sex gives you besides prana? It feels good.
So, no, it's not done the same way as Rin. Don't ask me why that is, or how it works, but Sakura definitely does not do the same thing Rin did.
"
Sakura's body still has after-effects from Angra Manyu.
Even with the contract broken, she's still a Holy Grail.
She was connected to Angra Manyu, so she's still connected with the other side.
Vast amounts of magical energy are collecting in Sakura's body, and she has to periodically let it out.
It's because of that magical energy that she can keep Rider, even after the Great Holy Grail's destruction.
But she still can't use it all, so she must be giving the surplus to Shirou.
Shirou's current body has a very weak Magic Circuit, so he would return to how he was before without her help."
There's literally nothing that says they aren't doing what Rin did, and even less that says that he needs poon frequently.