Question about be quiet! Pure Power 12 M

Hello Mims, I use this power supply with an MSI Suprim 3090, which also has 3x8pin connections. It works perfectly.
I think Asus means third party y-adapters because they can be of low quality and can burn out.

One should always connect to two separate outputs due to the passage of the cables. With three cables, however, this no longer matters, as the upper limit is not reached anyway. Go for it.😁