The audio amplifier approach has linear, fast acting feedback whose bandwidth is going to be greater than the frequency of the signal - 1600Hz.
The aircraft supply rectified and filtered its AC output voltage and then tried (with limited loop gain) to keep that result constant. If we think of fluctuations of current demand on the AC output in the frequency domain, we wind up with the concept of sidebands of an impedance function. The effective output impedance can be very low at small offsets from the 'carrier' frequency, and then grows rapidly away from it. In the time domain this means a regulator that allows large voltage variations short-term, but takes a number of cycles to catch up with things and to counter the droop or surge.
For a resonant converter these concepts cover the design of the resonant network, determining its minimum Q requirement and placing bounds on the permissible fluctuations of loads.
From a point of view of the design maths, a walloping great audio amplifier is the easy way out
. I speak from experience!. Maybe harder still was having to keep explaining it to people who hadn't been involved enough to have had to understand the difference.
David