Christianity does not have yanas. It does have sects: Catholic, Baptist, Mennonite. So when Westerners first started trying to understand Buddhism, they assumed Buddhist yanas were sects. Mostly this confusion has persisted, and even many scholars still get this wrong.

The relationship between yanas and sects is easy to understand by analogy with the automobile business. A yana is category of vehicle, like SUVs. A sect (or Buddhist “school”) is a brand, like Ford.