Busardo's test of the ipv Mini does show a "boost" on the SX330 of about an extra volt, for about a second, then a smooth ramp down to expected voltage.
http://youtu.be/nisQf54DnVc?t=25m5s
My thinking is that it's by design, since the later SX350 does the same thing, albeit with user control when using the firing mode feature.
And the ipv Mini/SX330 does a "simulated" step-down via PWM mode, also shown a couple minutes later in the video above. Goes as low as 1.5v at 5w on a 0.6 ohm coil.
The ipv Mini v2 is using the SX330 V2C chip and not the SX130 chip like the normal Mini however. It's the IPV2S chip inside the IPV Mini body basically. So I'm not sure if the V2C acts the same as the 130 chip. Can't recall Phil's output findings on the IPV2 atm and not sure if the S chip behaves any different. (Phil never tested the V2S or V3)