Personally I think that localization can be omitted from first-year textbooks, because its usage is relatively infrequent and its misuse causes no communicative breakdown.
When it is included in a textbook, it is (inadequately and nebulously) explained as something “taking place”. But this is not a fully accurate characterization. A better distinction of when to use ser or estar is whether the subject noun is tangible matter or intangible concept. For example, “Pablo está en la casa de María. ” Pablo is a mass of protons, neutrons, electrons, etc. He us tangible matter. In contrast, “La fiesta es en cada de María.” A party, however, in an intangible concept. A party has no atomic particles and while it can be experienced, it cannot be touched.
Of course, there are exceedingly ambiguous circumstances. For example, a song lyric by Annette Moreno says, “Hacia la cruz está Jesús, es el amor que buscas tú.” Some would validly argue that Christ never existed or that he did exist but no longer exists. So while Christ today is intangible matter, the subject noun operates as if it were physical matter. Similarly, a ghost in the house (“el fantasma que está en la casa”) is still estar because the subject noun acts as if it were an object.