Those features aren't even being used in this case, and they are not required. All that is required is the basic checksumming if the archive is valid or not, and all formats have this, including the meagre .zip.
As to the compression ratios, I think you'll need some numbers to back you up. Most sources say that .7z has the highest ratio (and is an open format). Here is one such source, but there many are others:
The .rar features you mention are/were important in a newsgroups setting, where you needed to split a large file into many parts, and before PARs came along. That was the purpose for using .rar at all.
Anyways, I see that you've linked to the rarlabs stuff, and indeed that is what I needed to do to unpack the archive (as in my first post).