Yes, but "Spain" isn't a Spanish word. The linguist in the book is making a valid point: Spanish isn't hospitable to initial s+consonant clusters, and usually inserts a preceding "e": "Esteban" ("Stephen"), "escuela" ("school"), "espero" ("I hope", from Latin "spero"). All well and good - but "sp" isn't a "smallest bit of sound that may change or alter meaning", since it's composed of an "s" and a "p".