Apple - Remove header columns in Page 5.0

In fact what Apple did here is better than before :

If you write in only one of these 3 columns it behaves as if there were only one column.

When you go to print, "truncated" headers will appear in their entirety on the printed page. It's just a glitch in the editing environment.

It helps to insert a text box in one of the cells. You can adjust its size, background, all styling and so on. The best thing is that this text box "overlaps" the header so it does not get truncated.