In some cases they do.

For example a GTK app main context menu can be triggered with F10. But this relies on the developer to correctly "tag" said context menu.

In simple cases it is obvious what to do, but in more complicated designs, where you may be able to achieve the same visual output in different ways, it may not be so obvious.

In that case, it is up to the developer as well to read and try to follow the published guidelines.