Looks like tabbing into a table puts the dotted box around the first table row irrespective of if there is a selected row in the table or not. To repeat this follow these steps in the TablePage of the explorer sample:
* Select a row other than the first row in the table
* Tab - this will take the keyboard focus out of the table
* Keep tabbing till the focus returns to the table
* When the focus returns to the table, the first row will have a dotted box around it. With each tab after that, the dotted box will move to the next row. Also, the row with the doted box does not have the inpit focus - using the up/down arrow key will move the selection to the prev/next row based on the original selected row in the first bullet above.

My expectation is that when one tabs into a table, the currently selected row is given the input focus. If there is no selected row, then the first row will have the dotted box around it. Up and down arrow keys will work of this row. The next tab will take the focus out of the table to the next component in the tab order.