Well...
False. There are a lot of nuances and factors to the definition of a "ninja" - the historical use of the skills of ninja as a political/insurgent tool of subterfuge and assassination is one aspect.
However for those involved in bujinkan for a long time - it is about mastery of movement.
The principles of movement taught by bujinkan are lightyears ahead of what you see in most martial arts. They are also subtle ad complex and easily confused.
BJJ is the modern Tae Kwon Do - the McMartial Art of our time.
There is a lot more to Bujinkan than comparing it to mercenaries.
Bujinkan teaches you how to actually be a better and more complete Human. It is much more than what the surface history teaches.
(I have been in Bujinkan for 20 years)