"There are a couple of possible explanations for this:"
You forgot one, That it was never intended to come across that the "End" was to occur in 1975.
Seriously, consider this. If 1975 was actually taught and believed to be the "End" why make all the arrangements to RENT the various stadiums, Coliseums and other venues for the 1976 district conventions ? If 1975 was to be the "End", who's to say those buildings would EVEN exist in 1976 ? And who would be around to collect the rent if it all was going to "End" in 1975 ?
"People tend to remember what they want about the context of the past events"
I agree. That's why I asked how much a five year old could actually remember. Why doesn't he mention the announcement for the district conventions to be held in 1976 ?