I strongly suspect that there is a bottleneck at available labor to deal with the reports, but I'm working on the following assumptions:
* more data cannot hurt
* some types of spam users go under-reported or not reported at all due to not bothering other users directly (they may get spam email, but delete it without noticing where the links go)
* my suggested method is likely to net some of said under-reported spammers
* it is the ones who are not bothering other users directly who are the primary cause of this specific Spamhaus complaint
* the reports can be dealt with one by one and suspended individually (I suspect the labor bottleneck is here)
* the reports may also be used as a data mine by their analysts