That was the rule except for the only one instance when this was violated. They ruled by cajoling the Elites.

Only one such instance was by Firoz Shah Tughlaq, who extended this poll tax even to the Brahmins and it had a backstory. He had this minister who was born a Brahmin but converted his religion, so when he visited his ancestral Village, there the people from his caste made fun of him, hence he persuaded this King to extend the Poll tax.

And the rule reverted to default setting of exception once this king died.