This is essentially correct. It's a little more complicated inside, and the expansion's really more like:

SELECT device_id, arrow_run_pipeline(timevector(ts, val), arrow_add_element(sort(), arrow_add_element(delta(), arrow_add_element(abs(), sum())));

The notable difference here is that this presents a lot more optimization potential, as the entire pipeline can conceivably be applied in one pass through the table.