In plus the sound engine was "Augmented" (or redone?) to handle MP3's and today's more "complex" Modules.

order.j2b loops at position 4? That's news to me... It always looped right back to the start for me in-game. Are you sure you are not overlooking position jumps?

Unless you are talking about how the music restarts when you die. That I think is a bug in the sound engine. It seems to always restart the music at position one, and It's noticeable when you are playing a module with "Action" positions like Neve.s3m