"Maybe it's a little different when it's not a Holy Grail War? Like the Rogue Servants that get summoned without a Master, or Chaldea's summoning system."

She doesn't know all the technicalities of it, though, the best she can do is describe the things she's seen and let him piece it together for himself.

"And sometimes there's cases of Servants getting corrupted and changed, even if the original version really was a hero."

You were this close to getting an explanation of how Gilles wishing on a grail created Jeanne Alter and kicked off the first singularity, be glad Ritsuka just plain doesn't know where to start with that right now.