Dbrim, you heard wrong or you remember wrong. See the Wikipedia article on the Jewish tailor Jacob W. Davis under the title “The birth of jeans”
Gavra, Rav Falk is known to be extremely machmir. This has been a hallmark of popular halacha books since Rav Neuwirh was forced to retract leniencies in the first edition of “Shemirat Shabbat K’Hilchata” after being attacked and threatened with a cherem on the book. Read “UNDERSTANDING TZNIUT: Modern Controversies in the Jewish Community” by Rabbi Rabbi Yehuda Henkin also. If you have a practical question ask your LOR.