It can be changed. I did it myself last week. On delivery, if I kept the key in my pocket and touched the drivers door, it unlocked but the passenger door didn't; since making the change, both doors now unlock. Someone has put photos of the exact location in the software where the option is:
According to manual published by our very own @AndyRC, cars without double locking system have this feature. Our cars have double locking system as stated on driver side window. BUT I can confirm we can still change it to unlock both doors, regardless the sticker on the window.
www.gr-zoo.com
Honestly, a lot Toyota dealers really need a kick up the arse about this. It says quite explicitly in the manual that these options can be changed at the dealer, so for them just to shrug and say "dunno, lol" is just not good enough, and to outright lie and claim they cant be changed is frankly pathetic. If they genuinely don't know, they should look at the manual then get on the phone to Toyota corporate to find out exactly what the procedure is.
I even responded to a guy on Facebook the other day who had been told by his dealer that they would charge him £70 to change these settings, and they wouldn't be able to do it until next month. Unbelievable cheek, it takes about 5 minutes to do.