the text in FAR 23 is misleading
If one is interested in what might have gone into a particular Type's certification, it is necessary to read, at the very least -
(a) TCDS to determine the rules applicable to the certification
(b) CAR/FAR relevant to (a)
(c) the relevant AC 23-8 which gives you the basics on what the FT certification community were looking at for the certification. There probably was a predating document for earlier Types but I can't bring that to mind at the moment.