Interesting. Is there an actual scientific reason for that?
Yes.
Brown Dwarves are too light to fusion hydrogen to the extent we see in "real" stars. I'd guess that the density of hydrogen available in that particular region of space is somewhat lower than what would be needed to create a full-sized star. If I remember correctly, the "arms" of the galaxy correlate to the distribution of matter in the interstellar medium.
Star formation depends on several factors, though, and this particular feature may have a different reason, I'm just making an educated guess. There are a numer of different "populations" of stars in different regions of the galaxy (e.g. neutron fields), caused by stars having reason to form very eary, to be very large, etc. Of course, different types of stars will be found in each population, but their distribution when you map then as little dots on a diagram of physical properties (-> wikipedia Hertzsprung-Russel diagram) will create a characteristic image that will let the expert say immediately "oh, this must be from an old globular cluster".
Ps: Anyone know if there are accessible globular clusters in the game galaxy?
