There was an article on LWN recently that reported on a conflict in the Debian community about librsvg. Rust's main compiler is officially supported on just a few architectures (x86 mostly, I think ARM is still not officially Tier 1?), causing problems for Debian on fringe ones.
Not that I necessarily think that this is a big issue. If macports decides to support discontinued macOS versions, they can do so on their own. If people want to run on fringe architectures, they may need to live without SVG support, which isn't a huge deal I think.