A family of Microsoft word processing software products for creating web, email, and print documents.
Well, that's interesting. If I clear that check box (in Word 2003), the two rows join into a single toolbar as soon as I close the dialog. I don't have to do any dragging or rearrangement. Since both those toolbars are almost the full width of my screen (and I also have another toolbar beside the Standard one), I can't see all the buttons, but they are definitely in one row.
At a guess, this may be some setting in the Registry. You might try deleting the Word Data or Options key to see if that makes a difference. See https://docs.microsoft.com/en-us/office/troubleshoot/word/issues-when-start-or-use-word for a description of deleting the key (after first exporting it) and https://docs.microsoft.com/en-us/office/troubleshoot/word/reset-options-and-settings-in-word for more specific instructions.