From Bahrych, Merino. Legal Writing and Analysis in a Nutshell 5th edition (2017). 343:
as. Do not use the conjunction as when you mean “since,” “because,” “when,” or “while.” Its broad and vague meanings can create confusion. For example, As a potential work stoppage threatened to block the opening of school, the arbitrators revised the wording of the contract. Does as mean “when,” “because,” or “while”?
https://www.etymonline.com/search?q=as doesn't answer my question. Incontrovertibly,
“since,” “because,” “when,” or “while”
are NOT completely synonymous. For example "since" can mean "because", but "because" can't mean "since".
More Examples. General Electric is the only company that has retained its place on the DJIA under its original name since
because the index's inception. When While did you last get your teeth cleaned?