1. Sure, I guess? I just don't see how Iva could get the idea of turning okama into women just to bait Sanji if he has no way of knowing that Sanji can't resist them in the first place.
2. Then this flashback would be just as missplaced as Zoro's. If those screams is what made Sanji think of Iva, then the Wano prostitute should have been the catalyst for the flashback.
IMO, Iva saw something else, like Sanji holding back even when in danger of dying, out of the kindness of his heart or some bullshit that connects to Sora and to him saving that mouse as a child. It would make sense to have Sanji accept the need to kill a quasi immortal being if that's the in-universe only way to stop their threat.