They use the same chemical formula but sometimes there are proprietary tablet/pill processes that a generic company can’t use. Or they choose different fillers. But it’s not impossible they’re just meeting the standards while the originating company holds it to a higher standard. I think most generics are decent versions and often the company keeps making it or partners with one of the companies making it generically so they can help ensure good product.

It’s probably like NYC pizza. Supposedly it’s the water that puts it over the edge and when you make the exact same pizza in a different part of the country, but with different water, you end up with varying degrees of different but similar pizza. All pizza, and all pretty close, but not all perfect copies. Now apply that to 30 companies in India looking at the same chemical formula and half-winging it without working with the originating company or any other generic producer to see what might be working better or not.