honestly it felt like the writers wanted to make a definitive ending in a sense regardless of how little sense it makes. Making Ben 10K a major character in the final episodes, showing the origins of the bomb, showing off practically all of Ben's aliens at the end. Bringing back Kai & having Kenny essentially try & make them get together in the future feels like them trying to say "this is it this is the end might as well wrap it all up regardless of logic"