I have never gone away for Shabbos Nachamu and have never heard of this trend from friends or acquaintances in my real life.
Only on imamother.
I think it is mostly for people who go by the Jewish calendar. Yeshivos and chadorim close down for "bein hazmanim" motzei tishabav and reopen rosh chodesh Elul. That makes Shabbos Nachamu the beginning of their big vacation period.
