Steve,
I've noticed this as well but don't have an explanation.
Once I drove to work of 46 miles & started off with 5 bands.
I parked with 3 left.
I started with 2 bars on.
Within a mile I was down to 1 bar and the fuel light on but still had about 45 miles to go and in a bad Atlanta neighborhood wanted to drive till the last one goes out, to a safer area.

(I hate how they place a giga-billion dollar business in these neighborhoods! Street dealers, ladies of trade, gunshots in the distance, right next to MARTA, Atlanta's "safe" public rail line)

I drove about 35 miles on that last bar before it went out, then filled with 11 point-something gallons of gas.

I remember once my wife & I started off near empty and after a mile or so 2-3 additional bars appeared.
She asked me why that happened and I simply replied:
"What do you expect, it's a hybrid car" (hee hee)

I've found the last 4-5 bars on the gauge to be less than reliable at times and in my case when the last bar goes out that's when I stop for fuel.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT