a sharp line is not what is required. in 2.79 there was never a falloff between a non weighted vertex and a weighted one, so the visualization is not correct in 2.8 since it can also have vertices without a weight that will produce a falloff. i would even go as far as saying this is a bug and does not properly represent what is configured.
and in 2.7 it looks like this if there are no active vertex weights which makes a lot more sense
