I suspected this was probably bogus. I don't know any biologist who includes origin of life in teaching ToE. They might mention the abiogensis experiments, but not as a theory.
That's one possibility, another is that they actually appear in the textbooks, but with introductory material about how they are scenarios suggested by evidence, etc., which Spetner "forgot" to include as the relevant context.
For example, on amazon.com they show the table of contents of Miller & Levine's "Biology" textbook, which shows an entry for "1-3 Science: "Facts" and "Truth", pages 15-18". Want to bet that this introductory material puts all later claims in the book into perspect with regard to how statements of scientific "truth" are always prefaced by an implicit, "the known scenario which best fits the available evidence is..."?