Observations from Helen Palmer's The Enneagram In Love And Work (which is one of the few enneagram sources that isn't depressing pseudoscientific quackery, and thus is highly recommended). She has some interesting insights that I haven't encountered elsewhere. WIP post.
Fives, as a type, can be prone to acting. The key aspect with Fives, though, is that these acts and personae are compartmentalized (as is true in general with Fives; they will "watch" themselves from a separate part of their mind). A Five will tailor-make an effective persona for a situation in order to say or effect what they want, while not identifying with the role or pose.
Additionally, a Five moving to Seven can adopt charming social poses in the name of appropriateness, or act on impulse without the lengthy prepare-observe-reflect process that typifies the Five, especially under stress and when they feel overwhelmed by choice.