Eecam,
I think we are splitting hairs, but nevertheless. If TOGA thrust is selected the A/C will only consider Vmo as the limit, and as you said will apply corrective pitch to limit the speed to Vmo+16kts. However, and I took this from FCOM 1.22.30.
"In speed/Mach mode the A/THR adjust thrust to aquire and hold the speed or mach target. The speed may be selected by the FCU or managed through the FMGC.
When in Speed/Mach mode the A/THR does not allow excursions beyond the following limits, regardless of target speed/mach number. For a selected speed target, the limits are VLS, VMax(Vmo,Mmo,VFE,VLE whichever applies)"
As you so rightly stated, better make sure you know what speed the A/THR will maintain, before you pull the TL to CL and the A/THR goes active. But on the other hand an active A/THR will prevent you from an overspeed.