That's what is special.
Currents often bring nutrients and water flow over the reef leading to lots of coral growth and fish. But mostly it's just that it receives much less diver pressure. The reefs along Sabang and Anilao have boatloads of divers on them every day, all day long. Verde gets a couple of boats per day and not every day.
As for 1 dive versus 4 dives, what he means is that in Sabang the boats typically make a trip for each dive. You go out at 8, dive, return to beach at 9:30. Head out at 10:30, dive, return to beach at noon. Rinse and repeat. The dives sites are not far away. You can still get in 4 dives, you just return after each dive.
Some like that, some don't. It let's you sleep late and catch the 10:30 dive, or lets you run to the room for fresh batteriesor something you forgot sooner. But some prefer to get on the boat and be done with it, climb up after the first dive and just sit on the boat and relax until the second dive.
Verde Island will be a single trip, depart in the morning and return late afternoon. Either 3 dives on Verde or 2 on Verde and one local on return.