Sounds like a vector/array/list in any other language after C++, like Go slice, Java ArrayList, Javascript array, Python list, Rust vec. Is there something I'm missing?
I think they're discussing the lifetime of that heap data, not whether the data is heap allocated.
I don't see them drawing any distinctions from C++ or Rust there either. It really sounds to me like most of their low-level experience is in C, where the contrasts they appear to be drawing really do apply.