Ashkenazim customarily read as the haftarah of Parshat Vayetze from Hoshea 12:13 until the end of the book.
As the ending of Hoshea is somewhat disturbing, Mishnah Berurah 428:22 recommends adding some verses from Yoel.
I have rarely seen this done in practice; furthermore, these additional verses do not appear in many printed chumashim.
In contrast, on Shabbat Shuvah (the shabbat between Rosh HaShanah and Yom Kippur), common custom is to read the haftarah from Hoshea 14:2 until the end of the book.
Again, Mishnah Berurah 428:23 says to add verses at the end (from Yoel or Michah or both).
In this case, common practice, as well as the printed chumashim, do comport with his ruling.
Why is there this difference in common practice? If it’s ok to conclude Haftarat Vayetze at the end of Hoshea, why is Haftarat Shuvah different (and vice versa)?