Fake RAM size isn't uncommon but it's rare to see 512MB configurations outside of industrial boards, even on older platforms like Meson8. I'd guess you still have the wrong boot ROM for the box and the RAM configuration in early boot code means it's only seeing 1 bank of RAM, and the second (missing) will add another 512MB to give a more normal 1GB.
Then again; this is an era where all kinds of shady manufacturing has been done. If it works and doesn't cause problems; don't fix it