I think you have missed the core of this bug report. (I realise that its name was misleading.)
If whilst you the date indicator is focused, you press the down keyboard arrow (and focus the calendar) then the left/right keyboard navigation breaks. Also, you cannot press the up arrow (which you might intuitively expect to undo the down arrow press).
Dear Javier,
I think you have missed the core of this bug report. (I realise that its name was misleading.)
If whilst you the date indicator is focused, you press the down keyboard arrow (and focus the calendar) then the left/right keyboard navigation breaks. Also, you cannot press the up arrow (which you might intuitively expect to undo the down arrow press).