Did he? "Liberal" didn't come into common political usage as a party name until after his death. The ideas were around as early as the eighteenth century, but didn't the phrase "classical liberalism" have to wait until there was some other sort of liberalism that had to be distinguished from the older variety?
The author does a good job of tracing the history and ancestry of classical liberalism. The problem is that romantic individualists, Whiggish politicians, anti-state radicals, and rationalist economists don't always fit under one umbrella. It's hard to imagine enthusiastic experimentalists or pantheists like Emerson or Thoreau marching under a banner proclaiming the iron laws of economics. This accounts for the intellectual troubles of the later Mill. What was radical in 1830 came to seem old hat in 1870, and anyone who prided himself or herself on being a "forward-thinking" or progressive intellectual moved on.
A revival of classical liberalism would be a good idea, but it has to be recognized that people and history will always want to evade the nets or traps that system makers of whatever political stripe want to confine them in. Classical liberalism would have to be more ecumenical than some of its sectarian proponents would allow. That's true of any ideology: there are the fervent, dogmatic core of believers and a much larger group who are influenced by the ideas and use them when they seem to fit realities and aspirations. To be sure the first group keeps the ideas alive, but the second group is essential to achieve anything in practical affairs.