Yes, that could happen, and the teller who advised that could be facing charges also.
The bank is in a quandary: Report too much (CYA SARS) and you end up alienating good customers. Don’t report enough- and you could face fines and/or sanctions.
Most banks err on the side of caution. However, it has been shown that the best thing to do is hire accredited experts, who then make the judgement calls. It is a little expensive, but in the end - safest.
The tellers do not usually make a decision to file a SAR, that would be unusual. They mark it as suspicious, and buck it up. An Analyst then decides whether to buck up to an Investigator. The Investigator, usually ACAMs certified, makes the call, writes the SAR, but often gets approval from the BSA Officer.
Yes, SARs go into a Database. Each SAR gets examined by a FBI or Treasury agent, sometimes very quickly. However, enough “that one doesn’t look too bad/ the amount is too small” SARS and yes, they all get re-examined. Generally, one “Stupid Structuring SAR” doesn’t mean much. Lots of people get SARS filed as they do something foolish to avoid a CTR.
If you get audited, the Auditor will have any SARs or CTRs in the file. But a CTR is not examined, nor does it trigger anything. However, they get checked if any sort of investigation calls up that name/ssn.