Thanks for pointing out how old GCC 4.8 is! You're right that a comparison against a later version of GCC is fairer - I've tested with GCC 5.3 (the latest I can easily get) and updated the blog post. (5.3 doesn't spot the missing coverage either.)
As others said, it makes sense for everyone to try different toolchains and see what works. It is possible to test newer gcc versions by installing in /opt or something, just make sure to get the right libstdc++ at runtime. With ABI changes, updating the distro gcc is too much trouble.