Chill, dude. Nothing is capital 'w' Wrong with your video.
Alekesu posted a video to help teach players how to boom and be less vulnerable to rush.
1-I assume both videos were made with the intent of teach and there was no opponent so map size is irrelevant.
2-If a player did an early rush of you with men then you did not have enough men to counter. If someone did an early rush on you with cav you could not counter. If a player did a cav harass on all your berries (which alekesu did not have) you would've lost all food production and many women (and therefore the game).
3-Great--that is why I posted the video.
4-No thanks, Alekesu already made one.
5-This is factually untrue. I've also never heard of a deadline for a rush.
6-I never knew all rushes come with 15 cav at minute 4.
More to the point--there are multiple boom strategies. I personally think Alekesu posted a very good tutorial that is a better for learners (because he didn't have the berries you did, he explains what he does, and it is at worst arguably a better boom to defend rushes with).