There's nothing like 'just fluff'

Fluff is stuff that doesn't have any bearing on the crunch (the actual rules construct) but does have bearing on the world and setting.
In this case, there is also the fluff of
"These full-body suits incorporate hard and soft armor integration with an ergonomic design that allows the user to move with as little restriction as possible"
and "Each suit must be custom-fit to an individual, tailored to her specific body contours and range of motion",
followed by the actual crunch where the effects are explained (namely: Bod x 3 as encumbrance limit).
This is in accordance to the passage "Tweaking Armor Encumbrance", 2nd bullet point on p. 44 Arsenal.
Personally, I only use encumbrance when a character wears more than one piece of armor. Cuts down on micromanagement and allows low Bod characters to survive a bit better.