I do not think Leonardo needed an assistant sculptor since he never completed any major sculpture.
Leonardo da Vinci was an painter, sculptor, scientist, sculptor, anatomist, mathematician, engineer, botanist, architect,...
Leonardo da Vinci considered himself both a sculptor and a painter.
Leonardo da vinci
He was a painter, an inventor, a scientist, but not really a sculptor.
Leonardo Da Vinci
Sculptor Musician Painter Inventor
He was a painter , sculptor , architect, musician, engineer , and a scientist.
He probably would have been, if he had had the chance to complete such a work.
He was apprenticed to Andrea del Verrocchio, painter and sculptor, in Florence.
That would be Leonardo from the town of Vinci. Or, if you prefer, Leonardo da Vinci.
Leonardo was a mathematician, architect, anatomist, sculptor, engineer, inventor, geometer, musician and painter.
No, my friend. That was Leonardo da Vinci.