This is because builtins are not part of the imports. All non-list builtin types are special-cased using stringToBuiltinType() in QQmlIRBuilder. The lists are not. When we get to the point of trying to look them up in QQmlObjectCreator, they aren't found.
|For Gerrit Dashboard: QTBUG-109147|
|446522,15||QmlCompiler: Fix recognition of builtin list types||dev||qt/qtdeclarative||Status: MERGED||+2||0|
|449127,3||QmlCompiler: Fix recognition of builtin list types||6.5||qt/qtdeclarative||Status: MERGED||+2||0|