Talking about non-necessary is IMO a cop-out: I bet we can verify systems with even fewer features that he is using, or just a different set of features that get him to the same spot. The interesting question is always whether a feature is useful enough.
You get into types at the end. And sure, we don't need static types. Just like, outside of verification, we don't need garbage collection, or bounds checking, or even loops. But are the features useful? What takes us to the goal faster? And remember that also changes depending on who is doing the tasks. A lot of differents in tooling selection, across all kinds of work, come down to preference, not general utility, and they sure have nothing to do with necessity
You get into types at the end. And sure, we don't need static types. Just like, outside of verification, we don't need garbage collection, or bounds checking, or even loops. But are the features useful? What takes us to the goal faster? And remember that also changes depending on who is doing the tasks. A lot of differents in tooling selection, across all kinds of work, come down to preference, not general utility, and they sure have nothing to do with necessity