Update: thank you everyone! user @Today has provided a great link of a discussion that suggests the correct answer is where being an abbreviation of, whereas as a replacement of since, hypothesized in these comments.
As I love archaic definitions, I’m more convinced to now that this is the answer!
Especially since the question originates from one weirdo using “where” instead of since.
https://english.stackexchange.com/questions/338694/is-it-ever-appropriate-to-use-where-instead-of-because-or-since
Like “Where we knew he was heading to Chicago tomorrow, we got on the first plane heading east to intercept.”
“Where we knew where the safe was, we began to cut through the wall in the corner behind her desk.”
Thanks
“Whereas” sort of makes sense there instead of just “Where,” but even that sounds like someone trying to be formal and missing the mark.
https://www.mentalfloss.com/article/652015/where-vs-whereas-how-use-each
Thanks, whereas is a valid hypothesis, good find.
These instances of “where” are used in informal conversations between characters as well, like in the example below, so while that’s probably not exactly it, it’s a good consideration.
“‘Where most of the animals are scared, I can’t see the point of scaring them further.’”