I reached out to the developers about this situation and confirmed that the PHP packages are built with version 2.11.1, so even if you downgrade the libxml package itself, it will continue to report the newer version as that is what PHP will use. However, since PHP was already built with the newer version, the PHP Info details will not update.
You mentioned there was a bug report on this - can you provide a link to that? I wasn't able to find that with my search.