It appears to be. I certainly have never heard of a 5.1V battery or a 4.2V
under load. I've been leery of false claims about battery voltage ever since the T-Rex was claimed to be 4.2V. [No ... it's just like any other fat batt: more like 3.4V.]
And consider the source. Any new breakthrough in
vaping technology I know of has come from (or been offered by) an ECF supplier. The eGO? Variable voltage?
juice-feeding? LR attys? Drip tips? You name it: all from those who
participate in the vaping community (i.e., ECF).