Health, “Just because it’s not mentioned in those Seforim doesn’t mean it’s Mutter”? Are you saying that anything not mentined in the Halachic codes is assur? It is obvious that all of the poskim knew about the Shalosh Shevuot. The fact they ignored them shows that they did not consider them Halacha but Aggadata.
Vochindik, with all due respect to the gadlut of the Maharal, he is a commentator and baal machshava not a posek. Besides, the Shlalosh Shevuot were said before the destruction of the Bayit Rishon. Apparently Ezra either discounted them or thought that the time that Hashem calls had come. In nay case, Rav Mei Simcha and Rav Soloveichik consider them to no longer be of any force or effect (if they ever were) as I have posted several times.