It'd be interesting to see how the distribution of sleep and awake times has changed over the last centuries. A decade or two ago this would have easily still been true but much less so since the typical nightstand alarm clock wouldnt have time synchronization. Further back alarms would be worse and worse so less true. I imagine if there's even church bells and specific hours when people need to work it makes sense awakening would be more tightly clustered than sleep time. I wonder when the trend would reverse if ever, maybe before indoor lighting but maybe before industrialization as a whole.