If you mean that sensors with a higher resolution (more range/detecting bigger ships) also are easier to detect (due to having more GPS, their emission strength), than that is still true.
The attached image shows three equal size (2.5HS) sensors of equivalent tech (10 active sensor strength, 5 em sensitivty), the longer range/higher res ones are easier to detect and your formula seems to be corret :-)
Edit: What was changed was the range of sensors. In VB6 it was linear, in C# it takes the 2D area covered by the scanner into account. As a result smaller/lower res sensors can generally see farther and a sensor that's twice as big can't see twice as far anymore, it sees twice as much area instead.
Compare Steve's post about the
New Active Sensor Model.