does one off topic board drag down the pins on my good boards

I run a gardening account and I also have one personal board that is basically a dumping ground, about 400 saves of other people's interior design and travel stuff, completely unrelated to the niche. Is relevance judged per pin and per board, or is there some overall topical coherence thing happening at the account level? I would archive it but if it makes no difference I would rather keep the saves.