While kde-base/plasma-workspace-4.4.5 had $(add_kdebase_dep kdelibs 'semantic-desktop?') kde-base/plasma-workspace-4.6.2-r1 reads $(add_kdebase_dep kdelibs 'semantic-desktop=') which enforces kdelibs to be build with +semantic-desktop, even if plasma-workspace is to be build without it. Reproducible: Always
No. It just enforces the same setting of semantic-desktop.