Q: Backing up to TimeMachine immediately after waking from sleep?

I realize that my Mac and many other Macs will backup to TimeMachine immediately upon waking from sleep. This seems odd since it's not like I was doing anything with it while it was sleeping. I would not think this is related to PowerNap b/c doesn't PowerNap backup during sleep anyway? (Not even sure if PowerNap is active on my computer).

Is backing up immediately after waking normal behavior? Can I turn set it to only do it an hour or so after waking?  Or is it simply because it missed the scheduled time machine backup according to the clock time?