The former was only used in the peculiar context of "/emul". The regular case is actually HERE pointing to RAMEND on boot.
This allows optional subsystems to not needlessly reserve too much system memory and it also reduces offsets bookkeeping.
This should help with the bootstrapping of non-emulated environment. For example, I have a problem with the RC2014: I can't send it bootstrap info until the ACIA is up. I need to find a way...