Standby Pass would only be available once the line hits a certain length. And once you book it, you would not be able to book another Standby Pass until that one is used. If there were so many people holding Standby Passes for ToT that the next window was 3.5 hours away, there certainly couldn't be that many people holding Standby Passes for the other rides. Why would you pick up a Standby Pass for ToT for 3:30 when you could get SDD or RnRC or TSM or MFSR for, say, 1? You wouldn't, and neither would anyone else, which is why this would never happen.
The bottom line is that none of these systems either create or destroy capacity. The same number of people would ride ToT with or without Standby Pass. Thankfully, Standby Pass will be free. The problem is with paid line-management systems, which inevitably cost all guests - either in money or time.