Fine, you want an explanation, here you go...
Essentially, the effectiveness of a surgical mask depends on two major factors: the location of the sick individual and the method in which germs are transmitted. Of course, in close quarters, a surgical mask may be particularly effective in preventing germs from being transmitted to uninfected individuals.
Ergo, when surgeons are in close quarters with open bodies it helps prevent GERMS not viruses to contaminate the body or sterile equipment.
Most people do not wear them correctly to prevent even germs. And they are absolutely non effective on a virus that small. Even n95 masks which would need to be fitted on an individual for proper sizing (not to mention they have to be clean shaven) don't protect against spreading or contacting covid.