The rules youre looking at is for open qualifier age is 18+. For play-ins age is 16+.

18+ for open qualifiers, 16+ for play-ins

The age for open qualifier is 18+, to play in play-ins its 16+. People kept cooking rocketbullets for no reason.
Red bull themselves invited Sentinels to play at their event even if it was 18+ they would still make exceptions for SEN