Haskell has String, ByteString and Text :) Data type proliferation is not confined to object-oriented languages (actually, since datatypes are much easier and cheaper to build in functional languages, they're even more likely to occur within FP).
The nice thing about Haskell is that you can have a million data types with different names, and as long as they're capable of implementing the type classes you are using, you can pretty much freely switch between the different underlying types. And if a library author doesn't provide an instance of a type class for the data type, you are still able to write one.
In most OOP languages, you'd be forced to either monkey-patch the classes, or writing cumbersome wrappers.
