^ My thing with Tart is specifically that, not even that she is a historical figure, that she is a religious historical figure and a Saint, I also play FGO and I don't ship their Jeanne with anyone for the same reasons, but that one scene made me go from "She is literal Saint, so this feels kinda weird..." to "Alright, Tart x Riz OTP! Let's go!".
The realization that this series really enjoys reiterating character archetypes, and that Tart and Riz are ultimately "historical Madoka and Homura" in the context of the series, also helped me to get on board of things.