is it CANON that the MC obtains ALL legendaries?
No because you can catch some legendary in more than one game
>>27503321
No, canon-wise no MC has a legendary except for BW protag.
>>27503369
What about Red, who canonically caught all 150 kanto Pokémon?
>>27503321
Latios and Latias are probably canon. Groudon and Kyogre are in a grey area.
As for the rest no, except the one from XY in which everyone acknowledges the fact that the legendary Pokémon decided to go with you.
The way I see it, they should add a different mechanic to capture legendaries, to make it seem more like they come with you out of their own free will.
>>27503321
Only the gen 6 and BW protags have canonically caught them.
>>27503385
this is gay, talking canon in pokemon is even gayer.