One of my friends routinely says things like "a woman has rights to his body" when speaking in English because in French possessives agree with the object not the subject, and the French word for body, "corps", is masculine.
In this case, since iPhone starts with a vowel, in French you'd say "son iPhone", so "his iPhone", perhaps.
Alternatively, in French you also always tend to the masculine form in the general case, so maybe that's it? It just strikes me as extremely unlikely that anyone would think, consciously or otherwise, that women don't have iPhones.
On your point about it being "extremely unlikely that anyone would think, consciously or otherwise, that women don't have iPhones", I was more referring to the older (20th century) authoring style where masculine references were used as a default rather than generalising such as "their iPhone".
[0] - "Anyone running html5test (http://html5test.com/) on his iPhone"