Other than the Chinese ique (since cracked), possibly some Korean stuff (unknown) and a few minor technicalities or more likely a ROM hack (some games released with English or other languages locked away and could be unlocked with hacking) no DS game was region locked. The DSi has some region locking stuff and obviously the 3ds does but not the DS (or GBA or GBC or GB...).
This then appears to be an alternative for EU serials, I have no idea if there is a deeper meaning.
There are several games that are byte for byte the same on the GBA between North America and Europe, if I there are any on the DS I have not seen them though. There are plenty that are probably identical in assets and most other things you care to measure things by (probably not filesystem or exact binary but close enough) but the serials differences will tank that.