Saw a photo in a magazine of a Cessna 182 cockpit. It had an EFIS panel. It also had a standard looking suction driven AH presumably as a standby AH.
The trouble was the standby AH was not only placed at the lowest centre part of the instrument panel but the parallax error would be significant. It would guarantee any pilot a real instrument flying problem if forced to fall back on it if the EFIS failed in flight.