Sigh... the difference is the same as I've been saying, this is just a word game. RotR is done by park closing. Other major rides are done more than an hour after closing depending on queue time. The park hours are not ride hours, and RotR is unique in that it has two hour shorter operating hours than other marquee attractions (thus, two hours of downtime every day).
The issue is you calling it 'downtime' inferring it's not running when it 'should' vs simply not running late.
If the park closes at 10pm, and space mountain needs till 11:30 to clear the queue... and Pirates only needed till 10:30... you don't say 'Pirates had an additional hour of downtime' because it didn't run as late as Space Mountain. This time is 'overrun' - not necessarily scheduled operating time. Yes Disney accounts for it and plans for it.. but it's not regular the operating window.
We all know Disney normally expects these attractions to run past park close and that impacts the maintenance windows.. and we all know Disney is trying to avoid that with RoTR. What people are taking issue with is you labeling that 'downtime' in the context of 'missing expected running time' instead of simply 'limiting operating hours'.