Apologies as I'm not super-familiar with Latin1 or how Python refers to Latin1, but it seems a little odd to even call it Latin1. It can be decoded as Latin1, but it can contain every possible byte, including 0x7f through 0x9f, which aren't really Latin1. It is human readable when pickling certain data types, but when others are involved, it sure seems like binary to me.

I think that is fine, and perhaps all that needs to be done is to update the documentation to say something like: "Protocol level 0 is the original pickling format. It is the default for Python 2 and is now a binary format; it originally was an ASCII format but this ceased to be true as support for new datatypes was added to Python."