Even if you want to accept a generation as spanning essentially two lifetimes with a small period of overlap, how do you determine when the overlap is to occur? Jesus said "this generation" will not pass away. Not "your generation" or "their generation" - "this generation." In the "primary fulfillment" of this, he was talking to his disciples and saying the current generation that witnessed his physical presence would not pass away before the destruction of jerusalem. In this case, if you want to apply an overlapping generation type thinking, the overlap would have occurred not at some point after he spoke the words, but when he spoke them. Someone born 10 minutes before Jesus made this pronouncement could be included in "this generation" and someone who died 10 minutes after could be included.
It's the same with 1914 - if there's an overlap, that's when it happened. We could consider all those who died just after 1914 to be a part of "this generation" and we could include all those born just before 1914 to be a part of it as well. So, in essence, this would be the generation doctrine that they ditched in 1995, which is why that one at least made some sense. They talk about a generation being a group of people who's lives overlap, which is certainly not a definition supported by any scripture, but even if you give them that, they're still wrong.
They're using two definitions of generation and mixing them up - one definition would be the people born in a certain time period, the other being people who's lives overlap in a certain time period and they're trying to say it's people born in a certain time period plus those who's lives they overlap with at a second unspecified time period.
It's just so effing stupid. It makes me so angry that anyone is stupid enough to just accept this as if it makes perfect sense. I get how people can be fooled by the explanation of the blood ban or about birthdays and I'll even give them the numerology BS that gets them to 1914. But the explanation of the overlapping generation nonsense is just so thin and full of holes (none of which require special knowledge/research to find as is the case with 607, blood, etc) that I just don't understand how anyone can listen to it and not be left with more questions than answers.