After enabling these features, I still end up with files in: /usr/share/gcc-data/armv6j-unknown-linux-gnueabihf/6.4.0/man/ Weirdly, I have all three "nodoc noinfo noman" set on two systems, one ended up with both man/ and info/, the other just man/. If it matters, I am generating binary packages on a build setup, then the target machines install those binaries with the FEATURES set. So, the .tbz files would include all the files, but they are stripped when installing from binary.
You should rather use: INSTALL_MASK="/usr/share/gcc-data/*/*/info /usr/share/gcc-data/*/*/man"
This seems like a limitation in portage.