Even though English is lingua franca(global language for two non native speakers) and considering that both of them work in film industry, its fairly easy to use English as the middle but not necessary.
Specifically speaking about their personal communication, here using English would not be as resourceful as learning the language your significant other is speaking and you dont wanna get lost in translation.
Personal experience (〜 ̄△ ̄)〜 my sister and her partner, they are a international couple and to my sister there is different understanding to language and culture of her partner because to her it not just a language more to part of her partner. She learns but more of a sides to her partner and language carries temperament, carries tones, and much more to it.
( ̄∇ ̄")To sum it up English is a major mediator in many important sectors but choosing to learn your loved ones language in its is act of love I believe.

It is good how the story is about two people who don't talk eo language, but did they never thinking of using English as the middle, or they didn't know English, but most people would know the basic english especially people who work in that industry
(sorry, I am just too logical)