A fluency heuristic in psychology is a mental heuristic where, if one out of two objects is processed more fluently, faster, or more smoothly, the mind infers that this object has the higher value with respect to what question is being considered. (Jacoby & Brooks, 1984)

It’s not very hard to imagine how this works with Kryptos.  If I’m more comfortable with substitution ciphers than tranpositions then I will allocate more importance and time to trying to solve K4 by some substitution scheme.

I would say this isn’t that negative in its implications for K4 research.  If there are enough people fanatically pursuing their own preferences then if the solution is to be obtained by one of these methods then one of the adherents to a particular style of analysis/solving will likely find the answer.  If a person is interested not so much in pursuing solution strategies which they enjoy then they must be aware of their own bias to select those methods which they naturally feel inclined towards.