I think the mention of the home button was because the back button on Android can sometimes function as a kind of task switcher (going from one app to another).Funny how most people here never had an android in hand. The back button function is "back". How is it related to the home button on idevices? Most iapps have a back button too, located in the top left hand of the screen.... I switched for a year to Android and having the back button at the bottom, always there is what I miss the most on my iPhone 6.
There may very well be some inconsistencies with the back gesture on iOS (especially with iOS 8, which I have found to be pretty buggy) but I can't say that I've ever really run into them in normal use. I don't think it compares to the implementation of "back" on Android where you really can never be entirely sure what will happen when you press it.
The real difference here is that the back button/gesture on iOS will never take you outside of the app you're using.