My 06 TL has 49,000 K and the rear discs are both scored. I'm told this is normal, as Acura's rear pads are 50% of the thickness of the front pads. Is this true??

 

Whoever told you that is an idiot for two reasons:

1. Rear discs scoring is not normal
2. Rear pads are not half the thickness of front pads.

Front (A/T) 10.3-11.0mm, Rear 8.5-9.5mm
Front (M/T) 8.8-10.0mm, Rear 8.5-9.5mm.

 

Agreed.

Mine had 90,000+ miles before I replaced them and I only replaced them to upgrade. They had no measurable wear and would easily have made it to 200,000 miles. I even shot temps of my rear rotors to make sure they were working.

I even went with Rotora slotted rears and the stock pads did fine.

It's somewhat common for the Honda rear calipers to stick on. Usually it's the slider mechanism and not the piston. You can take it apart yourself and see if anything is hung up. If it's just the sliders, clean it and lube it and it should be better. You could even notice a slight mpg increase.