This is not the case, except for the following fact...
Mode-S aircraft will not be displayed as bearingless if the aircraft is received as an MLAT/Mode-S target, in which case its position is plotted.
So logically, the addition of Mode-S/3D, will reduce the number of bearingless targets displayed.
The way to convince yourself is to take a look at the traffic page where everything captured is displayed, but not necessarily sent to the Navigation device
Thx
Lee