In the Dirshu Daf HaYomi B'Halacha email of 24 Tshrei, I read,
Reciting Shema in L'olam The pasuk of Shema Yisrael (and in some siddurim the entire first parsha) was incorporated into L'olam for those times when it is necessary to fulfill the mitzva of Shema at that juncture in davening (see below). According to the Gra, the complete pasuk is said only when attempting to fulfill themitzva during L'olam. Otherwise, only half the pasuk (Shema Yisrael orHashem E-lokenu, Hashem Echad) is said. The poskim discuss whether the passage should conclude with a beracha. (סעיף ט, ס"ק לא, וביה"ל ד"ה כי)
So the GR"A had a practice to break a pasuk up into parts, even a pasuk which is normally said as a whole (so I am not sure that any of the exceptions really applies because there was no intent to "use" the partial verse, as in exception 4).
How could there be a minhag to do something which seems to be an improper practice?