Ah maybe that would be an IxFx type afterall... if it's your own values that prevent your from communicating your others values... and you base decisions on idealism and feeling, then yea I would expect them to still be ethical. Keeping things to yourselves either to keep the peace or you just don't want people to know?
And yeah not everyone likes to verbally communicate what they feel and instead shows it through action, but this might be more of a Fi/Te valuing trait, if there's no emotional expressions or sentiments involved.
MBTI is about preferences not expression yea.