When rom files are dumped sometime you can get a bad read.
If they are send to the ipdb they are added "as is".
No checking, no verification.
The Pinmame files are verified in Pinmame to be working correctly.
Be aware, the ipdb files may be old releases.
Better (other or older) versions are found all the time and added to Pinmame.
Not all those files get to be added to the ipdb.
I used to send files to the ipdb, but haven't done that in a VERY long time.
It is hard to keep the files up-to-date on the ipdb.
Their updates aren't regular and have long spaces in between.
That is why I stopped updating the ipdb Pinmame files.
The best place to fine the latest Pinmame files is at http://vpuniverse.com/forums/
All Pinmame files can be used in real games.
Peter