Yep, Androids had big screens first, and yep Apple is copying that now because they believe enough people want a big screen. There is truth to the "one handed" argument, just as there is truth to the "bigger is better" one.
If you enjoy your big screen, you really do have Android to thank for that. If you choose not to remember lambasting Androids for having giant screens fine, but now you are no different than the Android fans who claim their first forays into smartphones weren't a blatant ripoff of the iPhone. Sure, it's worse what they did, but Apple is still doing a 180 on the "perfect size" statement they made even as little as a year ago.
It doesn't change that Androids are still a woeful experience by comparison, and that the user base of iPhones are much more loyal and statistically affluent, but it does prove once and for all that Apple never really thought 4" was the "perfect" size or they'd still be offering it as at least an OPTION for the 6.
By launching this way it's a tacit admission that Android had it right. I may not agree, but it is what it is, and Apple has made it's move.