They’re virtually the same. Georgism is a pillar of progressivism. Liberty does not fall from that tree.
George did not have one idea, the “single tax”, he had plenty of ideas. Like the nationalization of land, inch by inch.
Terms like progressivism and liberalism meant something very different in George’s day than today. It is hard to believe but back then, these concepts were moving society toward greater individual rights. Since then, these terms have been co-opted by neo-fascists to support the states complete domination of the individual. George believed in the autonomy of the individual, which could be a working definition of liberty. He saw the monopolization of land by a small segment of society as the primary bar on this autonomy. The land tax was his solution.
“Nationalization of land, inch by inch” sounds ominous, but what does it mean? George believed that individuals should use as much land as they want for their own purposes. However, they should pay society for that use. After all, society creates the value of that land. I can’t think of a fairer way to finance civilization. Neither could some famous “progressives” like Milton Friedman and William F. Buckley.