Exactly, it appears they are using every shooting where multiple people are shot. One the NYT used was an arguement/fight in a bar where a guy pulled a gun and shot three people.It's usually either 3 or 4 shot in a shooting. Some have more strict definitions, requiring 3 or 4 fatalities.
I think most rational people would think of mass shootings as things like today or The Pulse Club where someone enters some place of business and indiscriminately shoots people. One is to many obviously but we arent having 1 a day.