"can map A to B, solve B, and use that to solve A" establishes the pre-order A ≤ B; you seem to pronounce "A ≤ B" as "B reduces to A", which indeed lines up with the wikipedia page for preorders in general—"when a≤b, one may say that b covers a or that a precedes b or that b reduces to a"—but compsci pronounces that the other way around, as per the Reduction (complexity) wiki page: "The existence of a reduction from A to B can be written in the shorthand notation A ≤m B, usually with a subscript on the ≤ to indicate the type of reduction being used (m : mapping reduction, p : polynomial reduction)". As inelegant as the discrepancy may be, the compsci conjugation is much more common than the category-theoretic one, and this is a programming forum. Just think of it like an irregular verb.