The times are from the last 24 hours (or up to 7 days), they don't line up with the last time the phone was fully charged. So no direct comparisons could really be made given two different starting points (unless the last time you fully charged happens to be exactly 24 hours ago at that moment).
Oh dear logic really does go right past you doesn't it.
It wouldn't exactly be difficult to fully charge your phone, then come back after 24 hours to see the usage (and add up screen time). The "usage" stats reset on full charge, and the "last 24 hours" would therefore correlate in time.
iOS has always had tons of phantom usage anyway, but you seem to think background "usage" when the screen is off is fine - so whatever.
However, I would argue that the competitor (Android) is scrutinised by screen on time as a metric for battery life, so really Apple's "usage" stats are just disingenuous in this regard (and making stats available for the last 24 hours is just there to confuse users like this poor guy (quoted below) who swallowed your words as gospel and started harping about 'correlation' - what's the point in battery stats you can't correlate easily - saying that, like I said above you can just return 24 hours later for your battery stats to line up with your last full charge).
"Obviously" there is no correlation since they are different time periods. Duh.
""Obviously"" come back to see your usage 24 hours after you fully charged it if you want correlation? I mean, this isn't rocket science mate. "Duh"
Saying that - the whole "last 24 hours" thing is useless, it should reset every full charge. Apple are just scared to put in easy to correlate screen on time as their battery life myth quickly falls apart as people realise a lot of their "usage" is when the screen is off.