When inserting rows to a named table, upon opening the new file Excel asks to repair the file.
Repair message indicates Repaired Records: Table from /xl/tables/table1.xml part (Table)
The new rows do insert, but do not extend the length of the table to accommodate the new rows.
Reference to tableParts on pages 1698-1699, reference to Tables in general on page 1718, all in ECMA-376, 4th Edition, Office Open XML File Formats — Fundamentals and Markup Language Reference.