Furthermore, even for ascii sequences like b"file" the bytes do not map to the string "file" in every Unicode encoding - for example, in UTF-16 the bytes of b"file" represent "楦敬", which is a bit different than "file".
I thought Python was strongly-typed ? Am I incorrect in this regard ?
This behavior is a key requirement for all kinds of Python core data structures, for example, if you'd define bytestrings so that they throw an error when compared to a "normal" string, then this means that for a heterogenous list (pretty much all data structures in Python can be heterogenous regarding data types) containing both b"something" and "something" many standard operations (e.g. checking if "something" is in that list) would break because the list code would require a comparison to do that.