I'm sorry but there are flaws in your argument. If someone wants to enable Night Shift, they are probably in bed reading on the device, or using the device for whatever reason they want. Most people plug their devices in to charge when they are laying in bed. Therefore, low power mode would not need to be enabled, and Night Shift can be enabled.
Or, similar scenario. People are in bed reading, playing a game or what not, battery is down to 20% and they have Night Shift enabled. Considering they are going to plug their device in when they go to bed, they don't need to have low power mode enabled because that 20% will still give them 1-2 hours of battery life.
There is really no need to have both Night Shift and low power mode enabled at the same time. Give me one reason why you would need both.
I swear, people find the most obscure things to complain about.