What book made such a claim? That seems really odd and contrary to experience. Saying that we pronounce the consonant only once and don't pause is, shall we say, an uninformed way of talking about it. We don't pause, period. Is this supposed to refer to a propensity to not release stops before homorganic consonants (not just "the same")? Since [l] is not a stop, there's no released / unreleased distinction, so there is a false presupposition in the question.