It's a fictional universe, that's as good a confirmation as any. A lot of information on Marvel/DC character capabilities come from databook entries not in-comic feats.
No they aren't, you are 100% incorrect.
The information comes from comic feats not comic cards or databooks that list a static and general basis of their powers. Most guide books are not even created in house by the companies. Marvel has been known to use a "class system" in order to rank character abilities. Someon like Ben "The Thing" Grimm is commonly listed in the 85 Ton range, yet he's lifted well over 200 tons in his own title. Hulk is listed at the 100+ class but he's lifted over 1 billion tons.
And since you understand its a fictional universe, you should ALSO understand the point and usage of hyperbole. When a character is listed as "UNSTOPPABLE" it doesn't actually mean he is unstoppable, that's just his tagline. When a character proclaims someone has reached an unbeatable level, it doesn't actually mean they are unbeatable, unless specifically meant to be interpreted that way by the writer.