Interesting document
megan. Front page states Me 109, on page 10 the first paragraph mentions the 'BF 109 E'. I think this is a subject that we can argue about until the end of times and not come to a consensus. They switched designations at some point, probably related to restructuring the company as Messerschmidt A.G. in 1937. There was also the custom of linking the designation to the chief designer (see Ta 152 for an example) so perhaps this led to people calling it a Me 109 while the company tried to stick to Bf 109, before giving in and changing the name of the company to Messerschmidt. And then there is the already mentioned 'fog of war' that will have influenced a consistent strategy in designations.
I have seen similar discrepancies and variations for other, post WW II types as well. Getting everyone in a large company to call a product by the same name or designation can be difficult. Try starting a discussion on designations for Fokker built types
