actually, the reason why Saber remembers the past Grail wars isn't because of botched summoning, but because she's still alive and made a deal with Alaya, and not a spirit in the Throne of Heroes.
it is implied that Servants summoned in Extraverse (and Grandorder) remember their grail wars...
Is kinda a retcon, but at the same time, eh, not the biggest or worst one (most of those are related to our dear Saber lol)