Sorry for the slight delay in replying.
FILTER_ATTRIBS tells FormMail what each filter does.
It's stating what happens rather than telling FormMail what to do.
The values are very technical to FormMail and are not documented for that reason. We're pretty much the only people who create filters.
The "csv" filter does no encryption at all. And, yes, FILTER_ATTRIBS is indicating that because it doesn't have the Encrypt value shown for "csv".
I hope that helps.