Well, if what you described is true, then the datasheet should list the ‘minimum trigger current’, right? But it only shows maximum trigger current. I think there is a difference between ‘maximum trigger current’ vs. ‘maximum current’, in that the former refers to the maximum current that guarantees to trigger the triac, while the latter refers to the maximum current that can be tolerated. Also, to be honest, I haven’t seen any transistor that would only tolerate 5-7mA of current — that is rather small for any semi-conductor component.