I think both 5x5 and 6x6 is could coexist in the future if the last one will return as regular mode for Arcade at least.
But also “Free Role” option might bring more fun to the currently avaliable 1-2-2 and 2-2-2 (like 1-3-2 or 4-2 for example). Don’t sure about this option for Competive mode.
That’s not coexisting, like at all.
That’s just hiding one in a corner where barely anyone will realise it’s there.