Based on how he acts, I don't think he has any memories of a past loop or was reincarnated with knowledge of the book etc. so no. He does not know the old Judith. The only Judith Ruediger knows is the one he loves.
It kinda matters, it's the difference between "him protecting you because that's his upbringing" and "him protecting because of love". In the first case, Judith doesnt truly own Ruediger's heart, while in the 2nd case, she does. While the difference seem insignificant for readers, it's a big deal for someone in love who wants to exclusively 'own' his/her significant other as much as possible. The keyword here being 'exclusive', as in 'no one but me'. I think this chp conveys this beautifully enough, but the wording can still be polished to be less confusing.
As for why Luca's acting this way, based on what a novel reader told me...
The current Judith actually has the same personality as Luca's first run, but in that timeline Judith died/was killed and Ruediger's heart died with her. In some other runs, Ruediger didnt treat Luca as sweetly as the way Judith remembers rhe novel. Iirc there were also runs where Ruediger took out his Judith-related grief on Luca
My read on Luca's stance on Ruediger is that he is very grateful to Rue, but unsure about loving a father figure/mentor whose personality doesnt return the same affection back.
Damn. I liked this series when it was just a generic-seeming “villainess” story… then we started getting hints that Luca wasn’t what he seemed, which was a cool twist… now this element coming in is absolutely fascinating, AND we’re having REAL dialogue concerning the nature of care and love… this series is so damn good.