This post shows that iPhone has the same problem: every iOS version is a fragmentation point. If you want to support version X1, X2, X3, X4 etc. of iOS you have to make sure it works on all those versions, just like if you want to support version X1, X2, X3, X4 etc. of Android, you have to make sure it works on all those versions.
The post shows another thing: that while Google makes it easy for developers to support all OS versions by providing decent development tools (i.e. emulator that supports older OS versions) and providing developer-friendly phones (so that you can install different versions on the device).
In contrast Apple makes it difficult by forbidding developers to downgrade their phones for testing or providing emulators for older devices so developers have to jump through major hoops to make sure that their software runs on devices that are still being used by a nontrivial amount of users.
To summarize: in practice supporting multiple version of Apple's iOS is harder than supporting multiple versions of Android due to Apple's shitty developer tools and their general shitty attitude to developers, at least according to that one developer.