Didn't mean to cause offence, Fred.
The historical literature may well have been written before the advent of the piano, at around 1746.
From my experience I have found it almost impossible these days to get hold of a clavichord to practise on.
I came across one, which unfortunately wasn't for sale, in a tiny bookshop in Bonn some years ago. But none since.
My understanding is that keeping them in tune is quite challenging, much like a harpsichord.
And no keyboard can prepare anyone for playing the pedal board, apart possibly from knowing what the notes are called.
And no amount of traditional keyboard training can prepare one for playing a 'virtual' wind or string instrument, or indeed a virtual harp, etc., etc.
My fairly brief foray, when I was a lad, playing oboe and later flute taught me some of that, but not how
However I have added an expression pedal to the 560 which, when playing organ sounds, does go some way in emulating the swell pedal.
My second keyboard, a four octave MIDI controller keyboard with note velocity and channel after touch does allow me to play various virtual instruments.
But I have to say, it's not so good for learning technique, hence the 560.
A few years ago I picked up an Akai EWI 4000. Never did find a teacher for that one.