I will note that the Massachusetts, USA mapping community does believe that
there is a distinction between the two tags, as noted here:
https://wiki.openstreetmap.org/wiki/Massachusetts/Conservation
However, this usage and definition seems to be specific to that particular
community and is not a
Recently another wiki user marked landuse=conservation as "deprecated" on
the Map Features page:
https://wiki.openstreetmap.org/w/index.php?title=Template:Map_Features:landuse&curid=11273&diff=2071912&oldid=2068278
This same user had marked the page itself as deprecated back in 2017:
https://wiki.