> the PPC specific code that was created during the porting process to
> MorphOS3.x (and/or AmigaOS4.x)

As I said, LibreOffice is written in C++. Porting C++ code (or any other high level language code) from one OS to another has (almost) nothing to do with CPU ISA as that's what the compiler takes care of. And as I said, that's why LibreOffice is also available for PPC:

http://download.documentfoundation.org/libreoffice/stable/3.6.5/mac/ppc/
http://download.documentfoundation.org/libreoffice/testing/4.0.0/mac/ppc/

> not that AROS for x86/x64 could not also do their own port (probably much
> easier due to better tool chain(s) being available and not needing to cross
> architecture converting of the native Libre Office code).

The "native Libre Office code" is written in C++. It's of minor difference whether this C++ code gets compiled into PPC machine code by means of a cross-compiler on an x86 OS or gets compiled into x86 machine code by means of a native compiler on that same x86 OS. It makes no difference from the toolchain viewpoint, because PPC is a primary target ISA of the GNU toolchain anyway.
In conclusion, AROS for x86(-64) wouldn't have to have its own port, rather it would be one and the same source code for AROS/x86(-64) and AROS/PPC, merely and simply compiled into different CPU machine codes.
In general, you may want to read up on the concept of high-level programming languages.
(I remember we had a similar conversation half a year ago.)