I'm talking about the guts of it all, which are very dis-similar!
Such as? Changes can be solved using patches, this is the work you have to do in every distro (i.e. disabling / patching some stuff for mint target) and I'm sure they need to patch things, too. So what's the difference? They need some changes, we need some changes, we can easily branch when platform specific things need to be done within one patch-script. Or am I missing anything else?
To your latter mail: okay, but again, if we need to run some things native, they do as well! So if they can't compile using cross compiler, they have / had to solve it somehow. So you see, it's again about toolchain, nothing else.
Patching kernel, mintlib etc -- this has nothing to do with distro-depend part. You have to do it for gentoo, rpm or deb.