Let me comment, as a fully active Temple attending member.

This is actually not really accurate what is shown in episode 5. I get what you are saying though. It's actually a decent theory, but let me tell you why I think it's off.

First, Ron and Dan Lafferty were excommunicated for the LDS church. That is what this episode is showing in the case of Ron. Excommunication, according to LDS tradition, means that by the authority of your local leaders, you have lost all blessing pertaining to the covenants you have made in Baptism and the Temple endowment. Your "priesthood power" is removed. You are asked to remove the the temple garment and no longer wear it. While it is still your property, the tradition of proper disposal of the garment, as it is deemed a "sacred" thing, is that the symbols on the garment are to be cut out. Once they are cut out, the garment is just a t-shirt now without meaning, albeit with holes in it. Him still wearing the shirt with holes is a little weird, but it is also this show showing him as not really an anti-Temple ex-Mormon type. Also, your temple garments are typically the only white undershirts you own, so practically, if you were told to no longer wear them you'd either go undershirt free or need to go shopping and get new shirts. I think they are more just trying to convey this excommunication than anything.

Also, he technically didn't have to cut them out. He could have preserved them and tucked them away somewhere as some people who are excommunicated from the church do not actually leave the church, and the church doesn't have a concept of "shunning" people, though I suppose socially that can happen unofficially as people avoid others... but it is more believed that excommunication is a necessary path of repentance. Not saying you have to agree with this idea, just letting you know the cultural and religious traditions of the church. As such, maybe if he came back to the faith and repented from the error of his ways, he could receive his covenants again one day and put the garments back on.

I don't think the show was at all trying to have that shirt be an evidence of his new temple garment, because that would imply he went through some new ceremony through off fundamentalist "School of the Prophets" group to obtain it. It also doesn't really jive with the historical origins of the garment in the church, which is a little bit undocumented in the first couple of years with only a couple of accounts, but even if the very first accounting in 1842 mentions the garment was not worn, only stored in a home, before Joseph Smith's death, this was completely changed as there are many accounts of the garment by then as being modified and it was made to be completely white. So just a random shirt hanging in a clothes cabinet? I don't think so. It was the letter they were referencing probably, or just the author's error on the history of the garment, as the "Long John" style of garment, made of unbleached muslin was finalized, and the FLDS church still wears that style to this day and it is seen as an evidence of the mainstream LDS' drift from the original teachings because the ultimate design was changed in I think 1923 to allow shorts and short-sleeve clothes, and it has been through several iterations of new fabrics, and made fully white with bleaching.

I am still trying to understand why they say he left it there to protect them though. I mean, maybe he anointed himself as a prophet and declared the shirt as his new garment? I just don't see it at all, especially with it just hanging there on a hangar.

I appreciate the thought process on this one though.