Yes you are right that 2.5Ah and 3.0Ah compact pack would be limited in power
Here are some test of Sony VTCs:
VTC6 http://lygte-info.dk/review/batteries2012/Sony US18650VTC6 3000mAh (Green) UK.html
VTC5A http://lygte-info.dk/review/batteries2012/Sony US18650VTC5A 2600mAh (Green) UK.html
These cells can deliver 20-30 A in burst, min 400W of power with 5 cells in series, it's plenty of power for compact and subcompact drills and impact drivers. Surely they are not rated for sustained high amperage drain because of heat. Using such pack in angle grinder would be nonsense. But for protection there is PCB/electronics..
And i don't see any reason for using compact packs in X2 tools... Big high power tool needs big high power packs :-D