The results of this may be true, but if so, the results are quite sure to be solely based on average type of user and perhaps casing material.
Also iPhones are more likely to be used by people who couldn't be bothered to make a big decision out of their smartphone purchase, they just get what everybody else has and what they constantly hear about in the news and leave it at that. Hence many iPhones in the hands of people who aren't really thinking twice or being aware of the basics of treating hardware in a way that is less risky for it to break.
That many Androids have plastic as an enclosure helps mitigate the effects of a lot of drops, due to the flexibility. That alone could account for the difference, as all iPhones are built out of aluminum.
Points in case:
I've moved to Android with my last Smartphone and have the habit of getting my protection case and my protective glass *before* I purchase a new model.
In fact, the availability of a good/usable protective case and proctective glass is one of the criteria for me choosing a phone, a criteria and a purchasing order I recommend to anybody who asks me for advice when getting a new smartphone.
My girlfriend had a little red symbian Nokia touchscreen smartphone that looked like it had been run over by a tank. Twice. Cracked screen, parts of it not reacting, needing to remove sim and reboot at times - the works. I bought her a cheap current-day android 5 smartphone - red casing,
Her demografic for large parts is an intersection with todays classic iPhone user - not really interested in the details.
I'm sure this plays into the breakage quota aswell. You can say what you want about Apple, but saying that they build bad hardware is just being silly.
My 2 cents.