VTC5's are 30A batteries. That said, I'd be very skeptical that anyone has a legitimate source of VTC5's unless Sony has come forward saying they're beginning to manufacture them again. From what I know, they stopped because they realized people were using them in vapes, which was not the intended purpose of the battery.
Also worth mentioning, the Sig150 is capable of firing down to .1 ohm (42A) which no 18650 battery can safely handle. I assume the Sig150 won't output the amperage, and rather, will secretly lower voltage/lie to you in order to prevent frying the chip (chip has a 30A limit from what I've read). I've never heard of anyone discharging their batteries in a sig150, though its probably happened, but the rarity of it makes me believe the internal safety prevents you from pushing something like 40A to your batteries.