Without this XML file, the raw database is just a stream of random bytes. With it, you can identify that byte 00 at position 4 represents a player's overall rating, or byte 1B represents their weak foot ability.
You are not a modder. You just want to play FIFA with realistic sliders or a retro 2000s patch. Why should you know about fifa-ng-db-meta.xml ? fifa-ng-db-meta.xml