According to this paper (which I linked to), it looked in detail at a set of S > 1.3 Jy radio sources (274 of them), in a small patch of the sky, which makes me think that there are enough bright radio sources that 1.5 Jy wouldn’t stand out that much. EDIT: Oh you can’t tell the redshift of a radio source without looking at it optically, but that requires “determine positions accurate enough to establish optical counterparts” which can’t be done with the NVSS survey data. The paper linked above did it by using another more accurate radio survey to establish optical counterparts but that survey only covered a small patch of the sky.
According to this paper (which I linked to), it looked in detail at a set of S > 1.3 Jy radio sources (274 of them), in a small patch of the sky, which makes me think that there are enough bright radio sources that 1.5 Jy wouldn’t stand out that much. EDIT: Oh you can’t tell the redshift of a radio source without looking at it optically, but that requires “determine positions accurate enough to establish optical counterparts” which can’t be done with the NVSS survey data. The paper linked above did it by using another more accurate radio survey to establish optical counterparts but that survey only covered a small patch of the sky.