This article contains many theoretical assumptions that are masquerading as facts, but which have to be substantially reinterpreted on any dualist view.
1. Bigger regions are assumed to be more powerful.
Blatant materialist assumptions
1. we … develop theories about how personality is produced by the brain
2. [we can] figure out the underlying brain mechanisms responsible for personality differences
Statements which may (possibly!) have a grain of truth (if understood properly).
1. the size of certain brain regions is related to people's personalities
2. people's personalities are likely shaped by both genetic and environmental factors
3. A connection between brain region size and personality was found for four out of the five traits (but no statistical significance given!
4. a bigger brain region does not necessarily mean the region has better functioning
Statements which are probably true
1. many traits often go together and have grouped these traits into five overarching categories
2. Our experience can change the brain. And as the brain changes, personality can change.
We must have interactive dualism, not minds totally decoupled from the brain (otherwise we cannot sense or act in the world!). Therefore, when the authors ask "how personality is produced by the brain?", dualists should equally ask "how is the brain influenced by the personality?". Either might give correlations as described here.
In general, therefore, it is probably true that the development of the brain contributes to the development of the mind. The body and brain provide (I claim) a permanent 'basis' or 'residence' for the mind, so our mental development must depend on the full and healthy functioning of the body and brain.
Maybe size is important here. I suspect, however, that other functional factors are much more important than size. Connections and communications are presumably much more important than size.
Overall, dualists differ with the materialists here not about possible correlations, but about the nature and direction of the causation that is responsible for those causations.