Uneven rotor wear

In my opinion -- this is just something that happens with hybrids. I guess the brake pads don't get enough use and the rotors corrode faster than the pads can keep them smooth. If it causes poor performance, replace the rotors.

I've seen this in a Prius and also on my Accord Hybrid.

 

Did you compare the shape of the old and new pads? Maybe the aftermarket pads are not sweeping that rusty zone? Or the rotor dim's are different?

It's never occurred to me to use anything other than the car companies products, over the years, keeps it simple(r).

 

Yeah even on my cheap pads and rotors I get reasonably clean silver swipes . I. Using the ray estos burgundy labeled pads and cheap slotted X drilled rotors and these have been on car like 85K miles . Still look reasonably new

 

This is well within normal, you've been condensing and rusting on the edge, due to prevailing weather, colder temps, different humidity, different driving patterns. Not a big deal. Not going to change braking a noticeable amount. Still going to get good wear and life from the rotors and pads. I've seen 2nd gen with 250K with original pads and rotors look just like this. This mileage is normal unless you commute on a long steep hill every day.
A guess to what's happening. Overnight you get rust on the entire face. Next commute wipes the rust, but the inner edge rear gets the least force and the least heat so it doesn't always clean all the rust off and it builds/ accumulates sooner there because it's not fully cleaning every drive