Yes, this is correct. The B3s output waveform and so its tone quality is fixed. But this shouldn't matter for a beginner whose first priority should be learning to play in correct pitch with an elaborated aerial fingering technique and the second one learning to articulate the sounds with the left hand.
So, finally some years later, you might think about buying another instrument with an option to control the sound.
So, finally some years later, you might think about buying another instrument with an option to control the sound.