Well, I'm not really surprised Rider isn't involved in any ero. I'm sure Shirou will have enough problems with mana relationships with Saber. Plus, Rider seems more like the deliverer.
Sakura, though? That just seems odd especially given the in the Fate/Stay Night anime:
The shoujo-ai esque end bit in relation to Sakura and Rin
She doesn't have a servant.
I can follow the Infinite Blade Works route because Rin has Archer but the last arc makes no sense to me.
I'm glad there is no Illya poon so the whole cute relationship/crush she had with Shirou isn't ruined, but Sakura just is confusing.
I guess I could be answered with the question:
Does Shirou summon Saber as his servant in all the routes then?