Taekwondo founders don't say they are from Karate.
Actually, they do. Pretty much all the founders were trained in Shotokan Karate, with some additional influence from Northern Chinese arts and Judo.
Let's look at what the founders actually said about their training:
Chung Do Kwan - LEE, Won Kuk - Shotokan.
Song Moo Kwan - RO, Byung Jik - Shotokan.
Moo Duk Kwan - HWANG, Kee - Tai Chi and Kung Fu.
Ji Do Kwan - CHUN, Sang Sup - Kodokan Judo.
Chang Moo Kwan - YOON, Byung In - Kung Fu and Shotokan.
Now, it's true that YOON, Byung In did teach at the YMCA, and he did call his club the Kwon Bop Club. But he didn't train any of the other founders. He was known to be particularly close with CHUN, Sang Sup. They did travel and train together, but as peers and friends, not as teacher and student.
The original forms taught prior to the unification? The same forms taught in Shotokan schools, even today.
Really, you're just deluding yourself. Do you honestly think all the founders, who never unanimously agreed on anything, unanimously agreed to join in some giant conspiracy to pretend their training was in Karate? And that they somehow convinced thousands of students who were there from the start (and many of whom are still alive today) to join this conspiracy?
Do you want to tell us about the time you were abducted by space aliens, too?