is anyone using

spy_product_search_attribute_map

and can explain to me the benefit of that table?

I think it maps normal product attributes to specific fields. so it says this attribute should go to full text, this attribute should go to suggestions etc.

right. and I finally understood it. it can be mapped in ZED at

/product-search/search-preferences

and you can (as u said) map an attribute to e.g. full_text_boosted and are able to find products by searching for that attribute values.