> Some are inclined and some are not.
That is what "generally" implies, yes.
There is an argument that women are generally less inclined to negotiate due to the effects of sexism.
"Miller and Douglas discovered that women who had experience with successful negotiation were superior negotiators to men, even when they rated themselves as only average negotiators."
In the same vein, people who have never studied French are generally less inclined to join a conversation in French.
Which is a very specific use case of a specific environment with mainly unknown opponents (as opposed to work relationships, where you typically know the boss), tight deadlines (need a car immediately) and little wiggle room (shopping around car dealerships is time-consuming, sending resumes to competitors to test the waters is less so).
This blanket statement seems sexist. Some are inclined and some are not.
Besides, as soon as one leaves the world of small business, the corporations stick to salary bands attached to specific titles. The variations within the bands are usually driven by longevity with the company as well as performance reviews. It makes things easier in HR department, and creates a paper trail on compensation decisions in case someone decides to get litigious later.