It seems that we do "toStringList()" on a QVariant containing a string, which returns a list of size 1, in qmllint when reading paths from the settings file.
Only internal settings accept paths in qmllint's setting file format, there is no documentation and qmllint --write-default does not write those settings key out.
The affected settings keys are AdditionalQmlImportPaths, OverwriteImportTypes, and ResourcePath.