"Economy Delight" is a brand name used by VS and applies only to tickets they sell under the native VS flightcode.

You bought the flight as an AF codeshare. "V" on Air France is a deep discount economy fare class.

The "mapping" as you call it is correct; instead of directly transposing AF's very different hierarchy of fare classes to the corresponding letter in VS's very different hierarchy of fare classes, AF's Deep Discount Economy V has been "correctly" mapped, not to VS's most expensive Economy bucket "B", but to a much lower fare bucket.