Oh I’m definitely considering this canon.

SA Twily
TS What Shining Armor
SA NOOOOOOO
TS OH NO

@Background Pony #373C
You mean it could have happened in the day before the rehearsal scene.

SA: If you can’t accept the fact that I’m going to marry Cadence.  
SA: Then perhaps you should show up to the wedding in the finest wedding dress your friend Rarity can possibly design and ask father if he’ll walk you down the aisle.  
TS: WHAT?! ARE YOU SERIOUS?!  
SA: Of course I am.  
TS: Oh, you, big dumb-dumb! That was the whole point of my huge tantrum. I… I was jealous.  
SA: I know. I am your older brother, after all, aren’t I?  
TS: You sure are. And soon you’ll be even more.  
SA: I can’t wait.  
TS: Try, I promise I’ll make it worth your while.
 
Then:  

Oh if only that actually happened In the episode.

Snitch…

As an older brother myself, I can verify that Shining Armor was in a no win situation…