“There is not a single disagreement in the Talmud about core matters of Judaism. Each and every single dispute in the history of Jewish Law has been about a minor detail of the Law.”
While the first sentence might be true, the second one is definitely not, unless when you say “in the history of Jewish Law” you were still referring only up until Talmudic times. But anyway one can clearly see that since the Talmudic era there are many aspects of Torah which were lost/forgotten and many disputes even on major things.