A sakhi is a story about the Gurus, told rather than read, and it is how most Punjabi Sikhs learn the tradition before they encounter any text.
The sakhis circulate orally, in gurdwara discourses, in children's books and now in videos, and the version told in a household often differs in detail from the janamsakhi it derives from.
The baat is the folk tale told at night: animal stories, trickster stories, tales of kings and of clever daughters-in-law, with fixed openings and formulaic endings.
Both were told by grandmothers to children on a manji in a courtyard in summer, and both have been largely replaced by screens.
Punjabi folk tale collections exist, made by folklorists in the twentieth century, and they are out of print and were incomplete when they were made.
A sakhi is doctrine transmitted as narrative and a baat is a society transmitting its own assumptions, and both are being lost from the same room at the same time.
The sakhi is the account of an episode from the Gurus' lives and it is told with a purpose. The baat is anything else: a family, a village, a quarrel, a journey.
Both are performed rather than recited. The teller adds, adjusts to the room, and expects interruption, which is why no two tellings match.
The written collections flatten this. A janamsakhi on a page is one telling frozen, and the tradition it came out of was never one telling.