In your second screenshot, what if the show you had wanted to add was "The Conspirator" on Channel 4 HD (or any of the other 5 shows that run across 1am)? If the scheduler had assigned the original two recordings to different tuners like you wanted, there would have been no tuner available even though only one show was being recorded at any one time.
As sub says, the scheduler usually does a pretty good job of getting everything recorded, but it's not infinitely smart. The solution? More tuners.
server: NextPVR 5.0.7/Win10 2004/64-bit/AMD A6-7400k/hvr-2250 & hvr-1250/Winegard Flatwave antenna/Schedules Direct main client: NextPVR 5.0.7 Desktop Client; LG 50UH5500 WebOS 3.0 TV