I think he meant that Grogu learned that by himself through his own initiative, not that he must have learned it from Luke. Not convinced about that whole 2 year thing at all.
I wasn’t convinced about the 2 year thing either when I heard it . Came out of left field in regards to the two shows , but to me it hints at a reason , contrived as it was , to tie things into the proposed movie . I disagree on Grogu and his own initiative, I think it’s very possible that Luke would have taught him to step in and mediate peacekeeping like that . But we’ll see how things pan out