I feel like the answer FinCEN gave in this case is very nuanced and more akin to that individuals personal opinion on the matter (i.e. are you comfortable explaining this as your reason during an exam/audit?).
Personally, I go back to who benefits from the transaction(s). As these are clearly payroll check items and the employer is doing this service as a courtesy for them, then IMO you need a 2(b) for the employer and a 2(c) for each employee. I have had several commercial customers attempt this type of transaction but once I start requesting D/L + TIN info for each employee it quickly stops.
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...learning as I go.