Simply being told "How important is reliability and traceability?"
doesn't cut it with me, any more than pointing to the expiration date on
a tube of solder paste and saying "Never use this after this date!"

I want to know what, exactly, changes, and how it affects
reliability (I don't give a flying poof-ball about traceability as long
as the solder holds). I also want to know how these alleged changes will
affect the stuff in terms of making simple repairs with (mostly) PLCC's
and QFP's.

Well, then you go elsewhere to determine that (the manufacturer of the paste
seems so dreadfully obvious). Or, you just try the stuff and see what
results you obtain and see how many failures occur that haunt you later.

Geez ... this is a repair group. "What, exactly, changes, reliability" ...
you are expecting too much.