Here is some draft verbiage.
Could someone from the docs team please polish this and add it to confluence?

Freeswitch has long used a common parent directory for all its files typically "/usr/local/freeswitch".
A global variable $${base_dir} exists that configuration files have used to define paths relative to this common parent.
Freeswitch installs from Debian and RPM packages do not install files relative to a common parent making $${base_dir} irrelevant.
Since 2014-09-04 Freeswitch exposes discrete directory variables.
The example configuration files have been changed to use these new variables instead of $${base_dir}

If you build from source these variables are automatically configured but can also be set explicitly via the ./configure script.
Whether you build from source or install from a distribution package these variables can be overridden via arguments to the "freeswitch" executable.

Compatibility is expected because ${base_dir} has not changed.

To see the available configuration options "./configure -h".
To see the available runtime options "./freeswitch -h".
To see the values of the directory variables "./fs_cli -x global_getvar".

Sincerely,

Russell Treleaven