I had the same confusion reading this – what kind of go-based webservice framework can you discretely deploy new handlers without restarts/redeploys? Would be a really awesome thing to have!
(and lo, the BEAM does indeed allow hot code reloads. I don't think this is commonly used in BEAM-based Erlang/Elixir web services though. Certainly the Gleam people don't seem to like hot reloads very much...)