can a prefect flow's results be piped to another prefect flow using flow-to-flow?

You can pipe them by passing the results as parameters to the downstream flow … i.e.

@task
def get():
    return 2

start_flow = StartFlowRun(project_name="demo-flows")
with Flow("starter-flow") as flow:
    x = get()
    start_flow(
        flow_name="simple-flow",
        parameters={"x": x},
    )