https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97862
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> --- With r11-1967-g5acef69f9d3d9f3c537b5e5157519edf02f86c4d actually. The version you've mentioned started (properly) rejecting it, this wasn't valid in OpenMP 4.5, but is valid in 5.0 and for GCC11 the support has been added.