We are asking because both the Pistol and Duelling Pistol have the "Hand to Hand" rule, allowing for them to be used in CC, but the Warplock Pistol (and actually, the Crossbow Pistol, as it has a different rule altogether) doesn't, so there is nothing allowing you to use it in CC.
Veskit is a DP, who often break rules, and he is not using exactly Warplock pistols, he is using modified Eshin Claws with special rules. Actually, if you read the rules, he fights with 5 Str 5 attacks every turn, whereas if he were using the Pistol's "Hand to Hand" rule he would have 2 Str 5 attacks on the first round and then 5 Str 4 attacks every turn thereafter.