Now specialists are constantly improving their knowledge and undergo various recertification and training. The same doctors are constantly learning. So not only basic diplomas, but also certificates of additional education can be fake.
This is called retraining. In most cases, specialists are sent to such courses from the enterprise. Thus, these certificates of attendance of these courses are almost never fake.
Usually only the state organisations pays for the retraining cources. Doctors from private clinics visit such retrainig courses by themselfs. The same is with hairdressers, cosmetologists.