...a long time since I've been in this area...

David, I'm not completely sure which code fragments you're talking about for "revert or change".

Anyway: If I remember correctly, the confusion here is about the idea behind LDSHARED and BLDSHARED.
As far as I understand, this idea originally was:

LDSHARED: The "command to create shared modules". Used as variable in the "Makefile (and similar) templates to build python modules" for both in-python and third party modules. Initialized to hold the value which works for third party modules to link against the _installed_ python.

BLDSHARED: Read as "Buildtime-LDSHARED". Holds the value to override LDSHARED with while building python itself (_PYTHON_BUILD=True), which works for building in-python modules to link against the _builddir_ python.

So there's no point in ever setting BLDSHARED to the value of LDSHARED.

Actually there is no point in having BLDSHARED visible at all in an installed python, nor using its value while building third party modules - there's just no code yet that prunes BLDSHARED from the installed _sysconfigdata.py.

HTH,
/haubi/