What you're suggesting is not something that would need only an hour's exposition. It would mess with every scene where the other characters would want to say "remember the time you did X".
If a player wants to start from Season 2, there is no harm in them hearing "remember when you did X" because that just establishes to them that it's an important thing they've skipped over but are now getting the basic notes.
Thanks for the quote. I didn't think he'd said anything about 6.1 specifically being the starting point. I'm still unconvinced that it is the new starting point versus being a wrap-up arc preparing for 7.0 as the new launch point.
I know we're collecting codex entries now, but (particularly given that it's framed as your character making notes) that could just be to build up a resource for the new beginners to have dropped on them in one big lump later.
It's only a mistake if you assume that (A) it is the starting point and (B) the Scions are not intended to be ongoing characters in the new storyline.
If it's not the starting point, there's nothing to debate here.
If it is the starting point, and the Scions are continuing as support characters, then now is as good a time for an introduction as any.