Oh yeah, kid Gil wasn't as prideful or as tyrant as his adult self
That's why he didn't instantly went and said something along the lines of "This is something that I am not a part of, you foolish mongrel"
Servants who got reverted by his elixir experience change through physical appearance and mentally (how they think) which does align properly seeing as Artoria kept the secret from Shirou without telling him about it + she gets much more emotionally affected than usual
Wait, does that mean Sabertoria is actually older than Lancertoria?