Elden Ring

Title. I'm mid/late game and decided I wanted to try out some new weapons that I've been sitting on. Had no idea this attribute buff was the case but just spent some time farming my Faith up so I could try the SONAF that's been in my inventory forever. I realized my vigor strength and dexterity jumped by 5 and was confused and now realized it's only when SONAF is equipped. And it seems to apply to other weapons equipped at the same time? Or at least the attributes stay in place even.

How can I beat take advantage of this. Is there something I'm missing? If it's basically like having half of another radagons soreseal when equipped, maybe I need to beef my strength/dex a bit so I can carry the SONAF as a buff to other weapons, too!