Afaik, JA1 last official version is 1.13b (Sep 7, 95), and not 1.13 (Sep 5, 95).

GOG is providing the 1.13 one. The 1.13b patch changes the game's executable (JA.EXE) as well as 2 other files in the DAT folder (QUESTS.DAT and XRA.DAT).

When I tried the game initially, I noticed lots of horrible audio stutters during speeches while using the Sound Blaster 16 driver. I could circumvent that using the Sound Blaster Pro one, but I then noticed that game version problem. After installing the 1.13b, the problem disappeared while still using the Sound Blaster 16 driver. EDIT : After double-checking, this seems to be false.

So don't rely on GOG and manually apply the 1.13b patch after installing the game.

And there even is an unofficial 1.15 patch, but I haven't tried it.

Supposedly 1.15 nerfs some of the difficulty, which I've had no problem with.

Where did you find the 1.13b patch download?

After checking again, it seems I was wrong about the stuttering disappearing with the 1.13b version. It still happens sometimes.
So, the Sound Blaster Pro method is still a possible workaround.