A system is only as reliable as its least reliable critical subsystem
That's clearly not true, since error-correction mechanisms and redundancy can dramatically increase the reliability of a system even with less-reliable subsystems. Modify this, e.g.:
In many systems, depending on their architectural designs, a system is only as reliable as its least reliable critical subsystem. ...
In 6.5.1:
That's clearly not true, since error-correction mechanisms and redundancy can dramatically increase the reliability of a system even with less-reliable subsystems. Modify this, e.g.: