From what I understood, at present ulimited 5G Welcome offer is being given to all users regardless of their plan.
So at present ₹599 plan users will enjoy 4G and 5G data unlimited data. While other plan users will get Unlimited 5G, but 4G data according to their plan.
But after the Welcome offer is over, only ₹599 plan users will get unlimited data (4G + 5G). While other plan users will get to use data according to their quota.