different behavior of the tab key when cell navigation is enabled

[jcompagner]

see here:

http://plnkr.co/edit/sR1W3Dv08QgYUijHCzQ1?p=preview

if you select the first cell and then press tab, you jump right out of the list (url bar or something)

But if you change the code and allow also focus on the second column
then you can press tab nicely and it jumps from cell to cell to row to row

Why is there that difference between 1 or more then one column that is allowed to get focus?

[JLLeitschuh]

Probably some edge case that was not taken into account.