Hello Keith,
you are correct that the ABA Identifier causes false positives, this also happens for SSN identifiers, simply because the format does not have any checksums or the like to confirm this is really an ABA or SSN. There are two possible approaches for that, one would be to purchase DLP, which is indeed contextual aware when it comes to this kind of data. Another approach without DLP would be at least one more condition to the ABA smart identifier, i.e. a dictionary with words like "account", "transfer", "bank" etc. Combining both conditions with a AND statement (only if all conditions match) should work without causing much more false positives. That's after all how DLP works as well.
Hope that helped,
Andreas