As a guy who has had numerous friendships with varying types of women, there's a discord in approaching them the same as other types of friendships.
It's not a judgement of any sort, but there are women who when not engaged in a personal relationship will utilize male friends in masculine traditional roles. This creates the ILLUSION of a different type of relationship to outside parties and sometimes to the male as well.
For example, a 3 a.m. phone call to kill a spider because her boyfriend is deployed for 6 months. In reality, it requires a certain maturity and willingness to accept the role of substitute without stupidly engaging in other thought patterns.
However in fictional narratives, this is a breeding ground for sexual tension and intrigue with exaggerations of cliched behaviors.
So the deployed boyfriend, in fiction and reality, could easily be the trope barrier here.