Yes, the Ribbon in your screen shot is that of a Windows version. The tool appears as a singular
Insert button because the window shown is not sized sufficiently wide to allow the group of tools to expand... It's one of those that expands/condenses based on available space. If the window were wider the singular tool would grow to display
as a Group containing the 3 categories of controls tools: Content Controls,
ActiveX Controls, Legacy Form Fields.
Since Mac Office provides only Legacy Form Fields there is only the one small group to be displayed. The window typically is wide enough to display the entire group, but will condense if the width of the window is narrowed significantly.