To omit struts on the truncation plane, be sure to check the button 'Omit truncation plane' in the Struts and Hubs window.
This option is only available for Primal and Dual struts; Spaceframe struts are always omitted on the truncation plane as they crowd the hubs unecessarily and offer no structural or mechanical advantage because the dome foundation, (usually concrete) serves as the connection for these locations.
When struts are omitted on the truncation plane, always rebuild the hubs when using flange hub types (either ring or star). Rebuilding the hubs omits the extraneous flanges. This is shown in the following screen shots which depict a truncated 4V Icosahedral Primal and Dual with Spaceframe. The hubs and struts have been enlarged to make things clear:
Primal struts (cyan): 'Omit Truncation Plane' OFF. Dual struts (green): 'Omit Truncation Plane' ON.
Above: Primal stuts 'Omit Truncation Plane' ON.
Hub flanges are still visible for omitted struts.
Above: after rebuilding hubs, the extraneous flanges are ommitted.