Interestingly, he is admitting that umer changed the method of prayers. In sahih bukhari umer admits what a pleasant change he introduced (in the form of taraveh.) so the Taraveeh prayers methods followed today by muslims are not the one introduced by Holy Prophet (pbuh) and hence is not sunnah. infact it is a proof that most muslims are pursuing the sunnah of umer and not the sunnah of Holy Prophet (pbuh).