32r dual-stack subscriber limitation is due to 256k queues supported on chip (8 queue per subscriber), and this is hardware limitation. If you does not use hqos , number of subscriber will be bigger, but depends on filter used in service profiles / fib size / and some other options. So better way to test this for your specific use case.
P.S. MPC-3D-16XGE-SFPP not qualified for SM
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