Exactly correct,
as can be seen in your depiction, the fuel control switch(s) cannot be accidentally moved to ‘cutoff’ (they are protected on left and right by rigid guards. see the blue tab in the photo)
They can however, BOTH be placed in cutoff at any time .
Captain Steeeve showed a video, which he wasn’t sure was authentic, where one of the switches could be changed without lifting the knob as designed. But to me and to Captain Steeve the odds that both switches would fail like that is astronomical.
I believe they actually recovered the switches from the crashed airplane, albeit burned, and they still worked.
If one engine was cutoff, they probably could’ve managed to get into the air on one engine. Not sure about that though.
I believe it was a case of mass murder/suicide.