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
Yes, it’s used consistently to express “in the situation of…” the same way “since” is normally used.
This is a native English speaker from Colorado, but after looking it up, I don’t see any indication that some Coloradans regularly use “where” instead of “since”.
I never heard that when I was in Denver.
Everything else is written in standard English.