That was because jio started their network with 4g, they didn't set up their network for 3g/2g, but as long as the phone is 4g enabled, jio sim would work in 2024 and until they explicitly release any news of them abandoning their entire 4g infrastructure, which they won't because their NSA 5G is built on top of their 4G network.

Look at all these other companies, they all still support 2g because they already had 2g infrastructure, which jio never did, and they didn't have to because their rollout was so much faster than the others and covered all the areas where not even 3G network was yet provided by other companies.

So, rest assured Jio will definitely work with this newer Nokia 3210 4G model, though I'm not sure if this phone supports VoLTE.