By 'our' understanding, I maybe mean 'my' understanding, but my understanding is an unspoken rule or social convention that compels folk to be extremely hospitable to strangers due to the fact that they may be a deity in human form.
Now, we certainly have some social constructs regarding this today in modern western societies, typically based on empathy and "today you, tomorrow me" social obligations, and I am curious how different, or more accommodating and strict it would be. For instance, in our medley of modern western cultures I might assume this sub is comprised of, if one were on a hike and saw someone else on a hike in need, even if they were just hungry, it's reasonable to spare some food and/or chat for a bit. However, if someone comes to your home front door asking for that same granola bar out of the blue, you'd probably be less welcoming.
That's not to say that we do practice guest friendship, but there are situations where we certainly would be expected more so, and others less so, to be good to strangers.
Now, if someone comes to your door in classical Greece asking for food and conversation, I've been led to believe that you are obligated to accommodate this. How true is this?
It's likely that someone else can give a better answer to the question of what historical xenia looked like, and more importantly whether it existed at all, but I'd like to caution you against taking any aspect of xenia as depicted in Homeric epic as historical. Here's an answer of mine from June about the links between Homeric hospitality and a religious rite called theoxenia, and the likelihood that the human scenes are modelled on the religious rite.