JOSM Map Paint Styles

JOSM has a Map Paint Style has a “Mapnik (true)” style

The standard tile layer at OSM is a Carto Style but the current version of this style is not available as a Map Paint Style.

I would find it helpful to view how OSM would render my alterations before upload.

Is there a reason why the current Carto style is not available?

Obviously nobody maintained the "Mapnik (True) style for JOSM, the file was last changed in 2014. I’ve no experience with styles but it’s probably not easy to keep styles in sync?