In section 8.2.2 the last paragraph, preceding the schema fragment, states:
"The <table:table-header-columns> and <table:table-columns> element are very similar to [HTML4]'s <THEAD> and <TBODY> elements for rows."
Since [HTML4] has no such column structures and also does not have column groups, this is not meaningful.
Furthermore, there is no significance given to such groups in the provisions of ODF 1.1 beyond their definition and allowance in the schema, in contrast with the [HTML] provision for styling such collections in distinct ways. The ODF <table:table-header-columns> and <table:table-columns> elements have no attributes and cannot provide styling information of any kind.