>>36012815Adding a dual typing from a single typed pre-evo is just a catch all method. I'm talking more about things like how Shelmet and Accelgor have the same typing, but radically different playstyles and the former can be accompanied by Eviolite. Similarly, Clamperl can use the Deep Sea Tooth to boost itself and differentiate itself from Huntail and Gorebyss, who rely on more conventional item use and get Baton Pass.
Frankly, a slight difference in typing(especially when there's other fully evolved pokemon who do the same thing such as Tropius vs. Dartrix) does not feel substantial enough to even make me consider using the pre-evo. However, that may just be my inclinations like how people will use Braixen or Torracat just because they like them more than their evolutions.