One of the funky design choices made in the game was that there would be no character model. The obvious Doylist reason for this would be that the game was originally made in seven days, so excluding a character model saves time, but there's an in-game reason as well: according to the tapes, the game takes place in Reality-B, which is populated by the shadow-bodies of the humans in Reality-A.
What's more, the Reality-A/Reality-B thing explains why you simply respawn when you die: this is because dying in your dream only destroys your shadow-body — the only way to destroy you (including your memories!) was the Mindkill, which didn't work on you.
The point about listening to the entire series of tapes sufficiently often and in their entirety takes on extra meaning when you realize that, by the time you complete the game, you will have listened to every tape multiple times.
Similarly, the comment about some receivers having had firearms training, but new receivers having concentrated on learning the mind-tech needed to survive the Mindkill, is parallel to new players being clumsy with the firearm and experienced players much more skilled.
Word of God states that the Receivers are meant to be a realistic representation of a cult using a diluted form of Lifton's Eight Criteria for Thought Reform, except that they are actually right about their claims.