[ChrisFoster]

"Static" is a reference to the size of the arrays being fixed and encoded in the type. There's various allocation strategies, for instance StaticArrays.SizedArray uses a normal heap-allocated Array as the storage.

That said, the backing storage for the particular static array types used in this example (SMatrix,SVector) is an immutable Tuple which should generally be stack allocated if the library and optimizer are working together as intended. So the allocations here are a bit of a surprise; they may indicate a lack of inlining in something we expected to be inlined.