It can: using Hiccup or Selmer to render HTML (from data structures or from HTML templates, respectively). For the most part, that’s how we use it at work. We have one customer-facing app built with React.js that has a stateless service on the back end written in Clojure. We have several apps written in Clojure that do server-side rendering (three are customer-facing, three are internal-facing).
The author was just saying that it’s fairly common with Clojure(Script) to write an SPA (Single Page Application) that manages state on the front end and uses a stateless back end service – so you have one language on the front and the back.
As for the REPL, yes, at work we do all our development in/with a REPL and we start/stop the components of the app from within the REPL. To be clear, we do not type into the REPL. We connect our editor to the REPL (we use a mix of Emacs/CIDER and Atom/Chlorine at work) and we type into the editor and use a hot key to evaluate forms into the REPL as we work. Watch Stuart Halloway’s presentations on REPL-Driven Development and Running With Scissors for more insight into that sort of workflow (I’ll leave it to you to Bing/Google those so you can choose whether to read the talk transcripts, read the slides, or watch videos of the talks, since all those options are available I believe).