covered-table-cell

Hi,
I'm writing a Qt library for .ods files, available at:
https://github.com/f35f22fan/QOds

Can you please explain why one needs a special type
of cell (covered-table-cell) to designate the cells that
are next to the spanned ones?

I mean programmatically it's easy/possible to figure it out which
cells are covered, hence apparently the office suit shouldn't need a
hint for this.