Digital Wellbeing only takes into account actual usage/screen time, but the battery info report includes all and any event that used the screen. For instance, you can see that the FB use on both matches the 'screen time used', but Battery includes the additional 44 minutes it ran in the background.
I get that, I'm just wondering why there is a 4 hour difference between SOT. I know for a fact I wasn't on my phone for 9 hours yesterday ... Usually the two stats are relatively close with SOT.
If you have any pop-up notifications that turn the screen on or have accidentally kept the screen on while idle (i.e. button presses in a pocket, etc.), waking up the display to lockscreen and not interacting with any specific app, etc. All these can 'add up' and they wouldn't count as an actual app use.