Is a PLB the same as a 406mh PERB?

I listened to 2 interviews of the author of Lone Survivor.
He turned his military-PLB off to save batteries, when he was in
a poor locations. I believe he timed the "on" mode to satellite
position (overhead). He was also "on the move" so that might have
slowed his extraction.

I do not see the reasoning behind "not moving" criteria.
"He moved 400 yards in the last 4 hours so he must not need
help", is this an example of the SAR boss's reasoning?
Obviously, people, who are moving, can still need help.

I thought that a PLB may not always transmit position, for
example, a narrow canyon situation. But the position of the
satellite (receiver) or the position of the airplane (receiver),
in such a case, could be a starting point.