SBA and FEMA are two separate agencies.
True, but they are both part of the disaster triumvirate of fEMA, SBA, and ACE (Army Corps of Engineers). To file a claim with the latter two, they require you to first file a FEMA claim. FEMA vets the disaster, date, and your zipcode. They then assign a DR number which is a requirement of the other two and yes, separate, agencies.