Yes it's true, liquid waxes require more solvent. This is needed to keep the wax in suspension and so you don't have a large chunk of harden wax at the bottom of your bottle. It also helps in "remixing" when you shake before using.
The more wax or oil a liquid wax contains, the more solvent it has in it.
The more wax or oil a liquid wax contains, the more solvent it has in it.