I feel it was the only worthy ending of such an epic tale of antagonism. It was over even before it started, because all had been decided in their minds. Ben was momentary shaken when he realized Maul could read his mind about protecting someone valuable beyond measure, but it shows his intimate connection to the Force that instead of despair he got only more determinate and focussed. He used the decades to learn which Maul did not. Both Maul and Obi-Wan share a common link, they lost everything because of the other. Maul could never forget or get over it, blinded by his evil, whereby Obi-Wan - having lost his only true love to Maul - could forgive it and could live with utter dedication to his only remaining purpose in the tangible word: protecting the true Choosen One.
Did he lie about Luke? Well, Lucas would probably say yes. In his original Lucas tale Anakin is the Choosen One. But alas, Rebels was created by Disney. They made a fantastic animated series which contains a lot of hints to the movies to come. I strongly believe that with Ben's statement about Luke they were paving the way for EP VIII. We all know now that Luke has an insight about the circle of Jedi-Sith having to come to an end.
The true beauty of the last encounter between Ben and Maul was not the 3s-saber fight. It was the preceding conversation as well as the final liberation of a tormented soul. Because Obi-Wan did not slain Maul; he freed him up from the bondage of insanity and stayed with his Force-brother in his final moments. It was one of the most beautiful scenes in the Star Wars Saga.