I've had many games on Port Mackerel go over 4 minutes without a single cap. In fact, I just gave up on playing offense there, decided it'd be easier to just camp our own zone with Seekers. If my teammates get a lucky cap, great, if not, I'll force a draw if I have to. Actually managed to become the map I most consistently win (or consistently don't lose) on by taking advantage of how broken it is.
As for Blackbelly, it's easy to cap but almost impossible to hold for more than 3 seconds at a time, you take one point, they take the other, and then you run in circles going back and forth and ultimately getting nowhere. Nobody ever even finishes those penalty timers. Still a fantastic map for Turf Wars and Tower Control, but godawful for Splat Zones.