Probably because he doesn’t want anyone else to know about their strategy. It’s their rights to do so.
However, considering there will be so many players accusing their guild for cheating/exploiting (even though they do not do that) just because those players have less knowledge and experience about the game, AvantHeim are forced to reveal about how they could do it.
And now that people have seen how they did it, the video owner immediately took it down. You already got your proofs that they are not cheating anyway.
I’ve been in the similar position so many times with my guild, so I’m not surprised.
I’d say nice job to AvantHeim for founding that trick. I know that you guys are the top guild from SEA. I wish there is a way where we can face off against each other someday. GG and keep up the good work!