The interial various are really "instant display".

They record the information from the moment you turn the instrument on - which is probably when you turned the panel on. Therefore there is no concept of 'on' when switching to the A/H display. The gyros are used as part of the air model and are constantly calibrated by the external information including (in the Vaulter at least) the GPS.

In addition the one I'm familiar with has a built in magnetometer that calibrates to your installation and gives a rather nice always available compass.

Mel