Some DVD players, especially later, off-brand models, would ignore a disc's instruction to override the user preference. I remember the presence of these capabilities being a key feature in forum reviews of DVD players. Back then, the holy grail was an inexpensive player that had quick load and seek times, ignored region codes, respected user preferences and had analog component output (or a good composite/S-Video encoder chip). Based on these detailed user reviews, the community would arrive at a handful of players that were worth getting. These lists would be regularly updated as models would change firmware or chips and be sold under different brand names in different regions.
If you get a nice Magnetar, or even a decent Panasonic it will do it's best and work on DVD and non BD-J blu-ray, but it can't control what the vendor did and it will still fail for those Java discs.
Letting whatever dummy made the disk control the hardware to the extent that BD-J does is just ludicrous.