I agree that he's likely talking about delays. A lot of transactions need very minimal human input to clear a delay (usually misidentification since NICS is name-based). For firearm purchases, the NICS Section tends to clear these quickly to avoid default proceeds after three days. Since there is no deadline in the case of NFA firearms (NFA firearms are technically exempt from NICS even though NICS is still used by ATF as the background check on all NFA transfers), the NICS Section isn't very timely in clearing these delays.
But, this isn't the real source of long wait times. The 40+ touchpoints that exist in the extremely antiquated NFA process are the real problem. NFA transfers could easily be instant or near instant with available technology, but we're still sending paper forms to a bank where they are batched and then sent back to ATF for processing.