No, because the interop wrapper will create a default interface for you,
but it could cause the interop library to be quite large as it has to
recursively build interfaces for all of the .NET types it finds in the
signatures.  And if it runs into a type that it can't natively expose to
COM, it'll generate a paramter/type as simply "Object" and you'll loose
type information.

By creating your own interface, you'll have more control over the types
exposed to COM.