Not necessarily...don't forget that an extra FP would shift thousands of guests from Standby lines into FP side.
Imagine you're going to the Magic Kingdom. Your first 3 FP choices are the three mountains. When a 4th FP is issued, you choose 7DMT.
In theory, a 4th FP for everyone does mean more people going through the FP queue and fewer through Standby. But in many cases, it will also mean fewer people needing to use those standby queues in the first place. In the example above, instead of using Standby for 7DMT, you now have a FastPass. Throughout the day, the ride will pull fewer people from the Standby queue (due to greater FP %), but that's offset by fewer people waiting Standby in the first place.
The real question is what people do with the extra time they are given. Instead of standing in the 7DMT Standby queue, you have an extra 30 minutes to spare. What do you do with that time? Ideally for Disney, some of it will be spent dining / browsing / shopping. But even if the time is spent on other attractions, you may not be utilizing any additional park resources. If your goal is ten MK attractions before leaving, it doesn't really matter if you get through those ten in 5 hours with 3 FPs or 4.5 hours with 4 FPs. Your consumption of attraction resources (% of daily capacity) is unchanged.