EZP currently have:
"eZ Publish 5.next – This documentation space is work in progress and for the upcoming version of eZ Publish only."

This essentially means there is currently "no" documentation on 5.3 officially..

should be something like:
"This is the documentation for eZ Publish Platform 5.x. It mainly contains documentation unique to the new 5.x features while documentation for the eZ Publish legacy can be found <link>here</link>. For further info on legacy vs 5.x Platform, see <link>here</link>"

EZP52, EZP51 and EZP50 have:
"This is the documentation for eZ Publish 5.2. It mainly contains documentation unique to the new 5.x features while documentation for the eZ Publish legacy components is kept on doc.ez.no, as well as all documentation for earlier releases."

should be something like:
"This is the documentation for eZ Publish 5.2. However this is scheduled to be moved into the main documentation found <link>here</link> over the next months, so go there for most up-to-date documentation."