[clang-format] 'tab width' ignored

when using the clang-format plugin, the tab width is not taken into account properly when parsing system headers: i have set it to 8 in (a) code style/clangformat tab, (b) code style general and (c) text editor /behaviour, but nevertheless, they are set to 4 spaces

i'm seeing this on linux with libstdc++ (which is a bit annoying as libstdc++ uses a mix or tabs and spaces which assume tabs are 8 spaces).
the only workaround i could find was putting a .clang-format file into `/usr/include/c++`, which specifies a tab width of 8. but i'd assume that the clang-format is somehow not reading the settings from the default style