I can't speak for all the world, but in Ireland, a historic=wayside_cross is one that you would find in the Sites & Monuments Record. Usually a Latin cross, late mediaeval in date, not marking the spot of a death or burial. If it commemorates the War of Independence or 1798 Rising, it's a historic=memorial. If it's for a fatal traffic incident, it's a historic=memorial. If it's on top of a hill, it's a man_made=summit_cross etc.