You're 100% correct - "
/usr/include
" is the standard "system directory" under Unix and Linux. https://www.linuxquestions.org/questions/programming-9/where-standard-system-include-directory-is-defined-gcc-466068/
Error appears, but intellisense works #2179 microsoft/vscode-cpptools#2179
Check for includePath conflicts in settings.json vs. c_cpp_properties.json? #3733 microsoft/vscode-cpptools#3733