Fizz and Tahm Kench (Theory and speculation deals with time travel not for the feint of mind.)

So what would cause you to be miserable be the last of your race and have no answers on how the rest of your race disappeared. Well that happened basically to fizz. We never really got answers on how his race disappeared. If you have been told by a complete stranger he could show you the answers but you would need to feed him later on would you take it? Most likely. I'm of course talking about Tahm Kench quote to a taunt to any fizz "Wouldn't you care to travel to your people's destination?" but what if Fizz did accept this deal what would exactly happen or has it already happened?Maybe sometime Fizz did accept Tahm Kench's deal what would of happened. Maybe Tahm Kench lied and went back in time and actually devoured Fizz's race. Why can we infer Tahm Kench can time travel? Since of a taunt he does to an ally Ekko "Time is but another river - and I care not what water I swim in.".This is also comes from Tahm Kench being an enemy to Fizz and it has never been confirmed Fizz is a yordle especially from the Bilgewater lore update that just happened. But why did he not say about how Tahm Kench tricked him in his lore since the first part of his lore is from fizz since people haven't personally explored Fizz's race's home maybe because time traveling somehow wiped his memory I think it is because he is guilty since he accepted Tahm Kench's deal letting him devour his whole race. What do you Think about this theory?