Most of these boards have residency pathways. For most medical specialties completion of a residency is currently the only way to be recognized as a member of a particular specialty board. In the past physicians who had not completed a Residency program were eligible to take specialty boards based on many years of practice experience. This was done as newer specialties, such as Family Practice and Emergency Medicine, were established after many physicians had completed their internship year. These post residency training programs are called fellowships.
Fellowships focus more narrowly on a specific area of medicine within a specialty area.
Becoming a subspecialist can take from 1 to 4 additional years of training after residency is completed. It is required to both complete the selected fellowship and pass subspecialty board. Likewise, general medical knowledge may diminish in areas not related to a sub-specialists area of practice. The answer is no. That is they did not complete a residency but were permitted to take certification exams by their respective medical boards.