Is all-star rumble canon though? I mean, Examon is supposed to be the 2nd largest digimon, and here he's as big as angewomon.It's canon in All-Star Rumble. After Tailmon/Angewomon defeats Examon in the story mode, she gains Examon as an alternate evolution.
If a digivolution happens in adventure 1 (greymon->skullgreymon) then it's possible in every single other anime, manga, video game, etc. even though it is not shown.Yeah, you really have to define what you mean by "canon." Canonicity is fluid in the Digimon franchise.
Angewomon -> Examon techincally doesn't count as canon though since during battle you choose either to be Angewomon or Examon, rather than Angewomon -> Examon
Yeah this. I feel like most of the time that we're trying to decide whether an evolutionary line is "canon" or not is based off the theme or aesthetics, when from the very beginning of the franchise they've always had seemingly random Digimon at each stage for any of the starters you had. If I'm not mistaken, the creators have never said that all evolutions across the games or other media were not canon, so I don't think there's really a reason to believe otherwise.The original V-Pets had lines like Gabumon>Garurumon>MetalMamemon
I wouldn’t fret over trying to make sense of evolution lines in the wider canon.
I do think the anime at least tries to have more aesthetically sound evolution chains than the wider canon (You would probably never see a Biyomon evolve into a Leomon in any anime for example) however any evolution line released by Bandai is canon. Is it weird and nonsensical that Agumon can evolve into Devimon who can then evolve into Skullgreymon? Yes. Is it canon? Also yesThe only reason folks have hangups about "canon" Digivolutions is because we're so used to the linear Evolution from franchises like Pokémon that Digimon's Tamagotchi influenced branching system is completely foreign to fans.