Yeah, that sounds like the most plausible explanation. However, some of the memos have Killian’s [the Texas Guard commander’s] signature or initials overlapping with the printing, so that would mean CBS (or whoever produced them) going to a fair amount of effort to mislead people into thinking they were real. Oh, that’s assuming that’s actually Killian’s signature at all. If whoever produced them was just treating them as props, maybe they didn't bother to use an actual image of Killian’s signature.

The notion that they were created just as props is consistent with the very small amount of effort put into making them look authentic.