How is adopting another culture "inauthentic"?
Because it requires the intentional adoption and maintenance of dress, mannerisms and speech that do not come naturally to you.
Granted, some degree of change happens without intentional effort, simply from immersion in another culture. That's not what I'm talking about, though. It's the forced stuff people find embarrassing.
The "bad guy" in the hallmark special I just worked on was a pasta chef who constantly faked an Italian accent but was actually from Cincinnati. You're meant to find that out and go "wow, what a douche bag!" The underlying theme of the script is that authenticity is preferable in the end.
It's not very high brow stuff, being a hallmark movie. Presumably the producers believe as many will relate to that message as they do to the sentiments expressed in your average greeting card.