ARIA don't list aria-selected as default property for ARIA rowheader and rowcolumn what requires UA to not expose selectable state on these elements (http://www.w3.org/TR/wai-aria/roles#rowheader). Rich gave clarification: he said that usually column and rowheaders aren't selectable since the grid is managed rather by focus than selection. Selected column or row header means that whole column or row is selected. Marking as bug 2013q3a11y blocking since it's needed for get ARIA 1.0 shipped.
Created attachment 768951 [details] [diff] [review] patch
> Marking as bug 2013q3a11y blocking since it's needed for get ARIA 1.0 > shipped. it shipping is a pipe dream, but *shrug*