FAA publications are not always 100% correct they’re just the least amount of wrong.
As far as I’ve always understood is that overbanking tendency is a function of static/dynamic stability inherent to the design and the amount of bank used in the turn.
For instance a C172 will slowly roll wings level from a shallow banked turn while it will steepen the bank in a steep turn.
So it displays positive static stability up to a certain bank angle.
Past that bank angle you need a bit of opposite aileron.