A True Win requires two things: The pitcher must complete the game, i.e.
Note that this is very demanding: It's not enough to drive in more runs than he allows (because the other batters were partly responsible for those runs), or to score more runs than he allows, but to drive himself in more times than the other team scores.
It's a cool concept, but it's getting cooler every year; it made Syndergaard's start extremely fun, from the third inning on.
A starting pitcher would be more likely to hit one in a complete game (since he would bat three or four times), but even if we double the starting pitcher's home run odds, the chance of seeing an NL team's pitcher throw a True Win on any given day would be something like 1 in 15,000.
Nobody in history threw more Bob Gibsons than Bob Gibson.