Well, here, let me take 2 quick examples from the pop ups to show how they are unreliable as canon.
From LA X:
"If they can change the future / Oceanic Flight 815 will land in Los Angeles / instead of crashing on the island."
Note the use of the word "if". The very nature of it being there makes the statement a hypothetical.
"This is not a flashback / or a flash-forward. / This is a flash "sideways." / It presents what would have happened / if Oceanic 815 never crashed."
We know now that the sideflashes are showing us MUCH more than just what would've happened if 815 didn't crash. The lives of all the characters are different from a point far before flight 815, for example Desmond.
Basically, I wouldn't rely on the pop ups to do anything more than give you an "oh yeah, I forgot about that" moment.