Thank you so much for looking at this for me! I realize now the BuffFrame.lua thing I was looking at online wasn't up to date (even though it showed updated yesterday) so thank you for linking the townlong-yak one. I will just extract the Blizzard files going forward so I'm not wasting time.
I was able to get it working with the following:
Lua Code:
BuffFrame.CollapseAndExpandButton:SetChecked(false)
BuffFrame.CollapseAndExpandButton:UpdateOrientation()
BuffFrame:SetBuffsExpandedState()
I hope none of this is bad practice? >.<
It shows toggled hidden on login and on reload. Also seems to toggle normally without generating LUA errors.