Fake TAF or not, the same concept would apply if the destination had a non precision approach or similar.
Either way, in my region you could dispatch by factoring the visibility. If, for example, the destination had HIALS and it was night, the factor would be 2. So 600m becomes 1200m, thus above the minimum of 800m so you can launch.
edited to add that the 1200m is now what we call "equivalent RVR"