However the type explicitness is, IMO, one of its strengths. It lets you build up types that e.g. in C++ we're not a given, had properties about the behavior buried in docs, etc.
Thus even newbies get to bump into it quite fast.
The chapter that example is from includes the disclaimer:
> In this section, we'll cover the underlying structure of how Futures and asynchronous tasks are scheduled. If you're only interested in learning how to write higher-level code that uses existing Future types and aren't interested in the details of how Future types work, you can skip ahead to the async/await chapter.