Regardless of it's origin, your pennant is a beautiful piece and you should enjoy it. Please don't take my comments as an attack.
Detroit was a popular tourist destination in the early and glory days of the auto industry. These types of pennants may have been popular around holidays with Parades, during exhibitions, the annual Auto show (drew 10s of thousands of people each year), state fairs, conventions etc. and the Free Press would have had a presence at most if not ALL of those. The design suggests "Celebrate our City". Sure the colors are likely to suggest the Tigers. I just don't think these were likely sold at or around Tigers Stadium. The Free Press was THE newspaper of the day in Detroit and considering the popularity and success of the Tigers at that time I would think they would promote the team if that was the intent. Sure, the sports editor could have said "Hey Eddie, grab a box of those Detroit pennants we had made up for the Labor Day parade from the storage room and dump em at the Tigers game this weekend".
Tigers pennant manufacturers were some of the most creative and prolific of the early/mid 1900s and to compete in that market you would have to be creative.
Regarding the font. Here again there weren't a ton of fonts used back in the day and they used whatever was in the drawer. Old English was a popular font in the day and used on TONS of sport and non sport pennants, so if it were in that font you could make the same argument.
I don't have any pics from antique shops or flea markets, but I know Bob McCann had a couple of these for sale when he was still issuing sales sheets in the mail. I'll see if I can dig them up.
Hunts had one as part of a two pennant lot that sold for $80 in August of 2000. There isn't a pic on the web page, but here is the description:
Lot of two vintage Detroit related pennants: Early “Detroit” three piece construction pennant c.1910, unclear as to origin or relation to sport: EX and a Detroit Tigers pennant c. 1940-50’s: VG-EX
This oversized pennant is circa 1910 and even then the Tigers Head was used.
