In cruise in a A320, at F370 got direct to the FAF for a straight in visual backed up by the RNAV, and cleared descend all the way down. Had FINAL APP all the way from TOD till FD off at MDA.....
According to Airbus FINAL APP is designed to fly the vertical profile from final descent point. If FINAL APP is engaged too early and there are level off segments they will not be respected. DES is the appropriate mode to fly.