Tosafot (Berakhot 37a) inquires as to what should the closing berakhah be for one who eats wheat, a situation where the opening berakhah is disputed. The Rosh (#9) writes that if the closing berakhah is unclear, the food should only be consumed during a meal. While an opening berakhah question can be addressed by using the text of “shehakol”, this “general” status does not apply to “borei nefashot”, and only the correct berakhah would suffice. This view is cited by the Tur (O.C. 208).

The Knesset HaGedolah asserts that the intent is only that ideally one should only consume such foods during a meal, but if the situation does present itself, one should recite borei nefashot which (he adds in O.C. 210) is applicable to all foods. The Resp. Gan Raveh (klal 1, 15) understands the Rosh’s opinion to be that one should indeed not recite bori nefashot when it is not clearly called for, even when stuck in the situation, as it risks a berakhah l’vatalah; he himself, though, cites the Rif’s view that “borei nefashot does fulfill the obligation of “al ha-michyah” and thus when no other option is available, should be recited. The Magen Avraham and the Elyah Rabbah, however, are more concerned with berakhah l’vatalah and rule against reciting borei nefashot when it is not clearly called for.

The Satmar Rebbe (Resp. Divrei Yoel, O.C. 13:10-11) notes that since the concern is berakhah l’vatalah, all opinions would presumably agree that if other food has been eaten requiring a borei nefashot, that berkahah can be invoked to address the entire situation, as it is justified in any event. (See also Resp. Kiryat Chanah David, II, 29; Resp. Yabbia Omer, I, 12:1-5, and IV, 48:7; Resp. Sh’eilat Yitzchak (III, 19) and the journal Yeshurun (p. 382-387). Regarding the reverse question, “al ha-michyah” covering a need for “borei nefashot”, see Resp. Hitor’rut Teshuvah, I-II, 94, and Resp. Kiryat Chanah David, I, 33.)