This gets into theorizing a little too much so I'll just abstract back and make it simple.
This is my take on 'learning outdated Valkenhayn combos'
Learn everything about your character.
Your character is not a cookie cutter idea of how someone else is playing that character.
If you don't learn your character and really understand the priorities, speeds, hitboxes, hitstuns then you contribute nothing to that characters emergent gameplay.
Dustloop is about emergent gameplay and developing a character. It is not about emulating player X's play-style.
It is up to the player to incorporate their own playstyle and traps and reflexes into what the character already has to offer.
tldr; If you don't learn the 'old' stuff, it will be a lot harder to optimize and work in the changes yourself.