The difference is that mainstream liberal capitalism has decades of real world results across dozens of countries while anarcho-capitalism has nothing.

You can achieve the stated goals of anarcho capitalism or anarcho communism with policies that have nothing to do with these movements.

In fact the problem with anarcho capitalism is that the freedoms it provides are also the rope on which it hangs itself. It is the dodo of economic systems with no sense of self preservation.

Getting rid of the rope involves taking away some freedoms that nobody should have, but that would go against the spirit of both anarcho capitalism and libertarians.