And then immediately afterwards we see const T* in a supposedly immutable data structure meaning the pointer remains mutable. Yet another classic footgun.
It looked to me like most of the raw pointers in the blog were const. Sometimes you don't want the baggage of smart pointers and getting a cheap easily copyable view of your data is nice, so you want to return a const T. Usually if an API returns a const T I assume lifetimes are handled for me and that the ptr is valid as long as it is not nullptr.