How sound is Al-Albani's statement in "Al-Da'ifah" (1/101, under Hadith 71) regarding the description of "Al-Tatheen"?

Al-Albani mentioned the hadith: "The takbir is jazm" in Silsilah al-Da'ifah (The Chain of Weak Narrations), commenting that it has no origin as a Prophetic tradition (marfu‘) and that it is a saying of Ibrahim al-Nakha'i. The meaning of "jazm" is that it is not drawn out (extended), and it has no relation to the adhan. He pointed out that the adhan with this characteristic (i.e., making every takbir jazm) has no basis in the Sunnah. Rather, the apparent meaning of a hadith in Sahih Muslim, which describes the action of Umar ibn al-Khattab (may Allah be pleased with him), indicates that the mu'adhin combines every two takbirs.