$xwiki.getConfiguredSyntaxes() not equals to $services.rendering.getConfiguredSyntaxes()

When xwiki.cfg and xwiki.properties contains no clue about the configured syntax (core.defaultDocumentSyntax and xwiki.rendering.syntaxes commented), the list of configured syntax reported by $xwiki.getConfiguredSyntaxes() is xwiki/1.0 while the list reported by $services.rendering.getConfiguredSyntaxes() is xwiki/2.1
The first one is deprecated, but it should not be different than the second one.
Moreover, user upgrading their wiki from older version might end up having the first one used in the displayer of the XWikiPreferences class, since no update is applied apparently.