It is valid. But not liked. It takes the tension and focus and anticipation away from length of generation part of the prophecy. It is disappointing for older ones and for ones waiting for immediate pending relief but to new ones coming in and young ones that are into being involved, the explanation is not unacceptable or out of the ordinary.
Sounds more like an excuse to keep extending. Also, like when one thought he completed a task and and an inspector points reasons needed to keep working and go back to correct. That is what it feels like to people but nevertheless it is the only valid explanation given that the great tribulation will come using the year 1914 as a limit to the countdown. “Heaven and earth will pass away but my words will by no means pass away.” So it doesn’t depend on whether meaning makes sense but on the certainty of the prophecy—again based on circa 1914 generation being “the time of the end.”