Header Row, First Column, and Banded Rows checked in Word Table Design options. "Grid Table 1 Light" theme selected. Column and row headers are visually styled td elements, not th.
I've found another issue with VoiceOver and Safari involving <label> elements and the CSS display property. If a <label> is inside a table cell and has display: table, the input's label is not read, despite Safari's Node > Accessibility information displaying the correct label.
HTML <table> elements are meant for tabular data, not for creating two-dimensional layouts. However, OpenScholar's only other non-code solution to have content in columns is to not write it in a Page but to write each piece in a Custom HTML widget and use the Layout to arrange them. Content in widgets is much harder to manage than content in Pages (or other post types).