Wich follows the same rules as any other skillcheck.
Maybe you mean "Highest value curently presented in EA" ... ?
Feel free to prove me wrong by submitting a screenshot of
an actual CHARISMA speech check during dialogue requiring a roll
higher than 20 within the
Early Access in the current
4.1.1.1755403 version. This should be pretty obvious, as the feedback is always solely and exclusively based on experiences within the current Early Access version.
Otherwise without proof this is just a pointlessly nitpicky off-topic debate, which I will not participate in.