When the account says "will not PASS away" it defines a TIME period. but it uses a human life-span as a chronometer, a clock, - not the most accurate one.
when the account says "all these things" it defines what HAPPENS during the end times, and the wt 'Armageddon' is the end of the end, it is included, (although not mentioned by name) in "all these things.", the events.
wt writers, by making it the 'anointed' generation rather than the generic, normal one, made a really wrong move and
by predicting that this 'anointed generation' would die BEFORE the end of the end clinched their anti - truth* revelation.
* if the work of the later BIBLE AUTHORS can be defined as TRUTH, starting with the talking snake.