Reductionism can mean either (a) an approach to understanding the nature of complex things by reducing them to the interactions of their parts, or to simpler or more fundamental things or (b) a philosophical position that a complex system is nothing but the sum of its parts, and that an account of it can be reduced to accounts of individual constituents. This can be said of objects, phenomena, explanation, theories, and meanings.
Do you know the story of the blind people feeling up an elephant? Depending on who tells it, a varying number of blind or blind-folded or stand-in-the-dark people each explored different body parts of an elephant. The person touching the leg was convinced he's touching a tree. The person touching he tusk thought it was a pipe. The guy with the tail thought he had a rope, and so on.
The Holistic world view, on the other hand, says the whole influences functions of the part. Again, thank you Wikipedia:
Holism (from ὅλος holos, a Greek word meaning all, whole, entire, total), is the idea that natural systems (physical, biological, chemical, social, economic, mental, linguistic, etc.) and their properties, should be viewed as wholes, not as collections of parts. This often includes the view that systems somehow function as wholes and that their functioning cannot be fully understood solely in terms of their component parts
Type experts like Linda Berens make a point to underline that Type preferences show up in a pattern. The pattern is more than the sum of its parts. Looking at the whole and understanding the dynamics behind the four-letter code provides a richness that looking at individual functions simply doesn't supply.
More than that, it gets real problematic when we take the four-letter code apart and start talking about "Thinkers" or "Judgers". No wonder many people still believe Type preferences put them in a box. Unless our language gets more precise in reflecting that the functions describe the process of how we use our brain, it'll be hard to convey that Type knowledge is helpful to promote growth, not stifle it.