It is yes, and I'm aware of that rule... I wouldn't be too surprised though if they have another rule at the ROAR stating that they don't accept front wheel driven cars at all...
Whatever the case is, rules may be open to change, and if that's not the case it might be possible to bypass them... but if it's only the shorty that is a problem, it's easy making a saddle-compatible version
I know it's not everyone's cup of tea though to use shorty packs - definetely something to consider, and probably therefor something to work on later on anyway.