The problem is you are incorrect. The deeper your knowledge of music theory, and the more experience you have with a capella choir music or certain instruments where they can be played differently, The more apparent this will become.

Trying to sing a D# in a B major chord the same way you would a Eb in a C minor won't be a great experience.

Most of the adjustments will happen automatically if you listen to your fellow singers and have experience. But they do happen.