This forum is deprecated.
The RAD Studio main help (invoked from the IDE) is titled "Help for RAD Studio 10.4 Denali"
Using the index to find VERnnn Compiler Versions doesn't include 10.4 it only includes 10.3 (and earlier)
'What's new' also delivers the narrative for Rio (10.3) clearly the Help authors have not yet caught up. Having said that there is more than enough information in that regard on this website. As for the version number the usual practice is to bump it up by one from the last version.
But your implied point about Help being effectively out-of-date is in my view well made.