There is an updated version of Ace Combat 2. While the original version (let’s call it 1.0) was released in April, the updated version 1.1 was released in July. The main difference is in the English translation (diff shown above).
Apart from that, the original version contained the leaked string
04EAS.PLY P:\UNIX\PX201\BRIEFING\WO which was zeroed with the update. Executables are different as well, but I didn’t bother comparing them.