sounds more like a rubbing cutting compound, to me,
if you want to remove swirl marks use g3
if you want to remove contaminates with out removing a layer of paint/clear coat use a clay bar
there is no substitute for doing it properly i cant see how it can be a liquid clay bar and how it works since propper clay pulls bonded contaminants out of the paint ant traps them in teh clay bar... I would assume the "liquid clay" is an aggressive polish which polishes or shears the contaminants off the surface of the paint so it feels smooth..
as for polish Hiding swirl marks.. it depends on the polish Some polishes contain a cutting compound which work by removing the top layer of paint hence removing swirl marks others contain "fillers" to hide swirls..