boring7 wrote:<tf internally driven?>
Certainly there is some of this going on, though a lot of it is the misprogrammed nanites and their controller system desperately latching onto anything it detects nearby to provide it with some direction. Sometimes that comes from within the infected individual, at other times it's something external, and other times it's seemingly random with the machine instead activating according to an instruction set it either already had or just created elsewhere. The latter only really applies to the spontaneous changes which affected many survivors in the initial moments of the outbreak as the nanites went haywire. The transformations in this outbreak area are very sexualized and mostly animal-driven because of reasons, but that is not always the case. While I'm less familiar with the canon for other areas, I know there's variation between how the infection has manifested itself in other areas. The one that comes to mind is a robotic area populated by aggressive machines.
I'll just add that you can't always trust the 'expert opinions' of the more informed or scientific NPCs you meet in the game to be fully accurate. At times, they are presenting theories based on conjecture or their own limited experience and experimentation. Some of what they say is true, or at least partially true, but not always. This is why there's some contradiction between their views as to what's going on and what's to be done about it.