How did I know this thread would either be about exhaust parts or brakes?

It's normal on any car... even new ones. It's very difficult to rust-proof an exhaust manifold. It's a cast-iron part that gets glowing red hot during the normal course of operation. Any coating you put on will eventually flake away, so they don't even bother.

Exhaust manifolds are thick, cast iron parts. We will all be long dead and gone before it rusts all the way through.