He wanted Sindhudesh within Pakistan. He was an opportunist he just wanted to let go go Hindu control of money in Sindh.
To see what an ethnonationalist movement actually feels, look at what the foot soldiers and mid level management says, leadership doesn't reveal "true" feelings. For example, Sorath Sindhu on twitter reveals what a lot of JSQMwalas feel. Among PTM/NDM/ANP/PKAMP circles there is a lot of talk about how Pashtuns of Pakistan are becoming "desified" and how we aren't sticking to our culture and women are marrying non Pashtuns yada yada yada. Basically alt right talking points.
They lament that ANP during its tenure wasn't as aggressive as PPP was for language. They also are envious of the fact that GM Syed created a long lasting conscious for his people, while Bacha Khan and Faqir Ipi failed. So there's a respect from PKMAP/PTM/ANP/NDM circles towards Baloch ethnonationalists and Sindhi ethnonationalists as well as Saraiki ethnonationalists.
Cultural preservation is a myth, if someone from Lahore in 2022 goes back in time to talk to someone from Jalandhar in 1922, there's going to be an obvious difference. And if someone from Peshawar from 2022 goes back to talk to someone from Jalalabad in 1922, there will be differences as well. Even the way people spoke wasn't the same back then. Cultures change, grow, and evolve.
The most important thing is focusing on the things that matter, like development. Religion seldom changes, but culture always does.
Ethnonationalism never comes with rational thought.