Whether the number is more than that of victims to date who can recreate this? Who knows
Other victims whose data were encrypted by the same malware (before any updates) could benefit from this disclosure to try to recover their data.
New versions of Akira and any other ransomware are constantly being developed. This code is specific to a certain version of the malware.
As noted in the article, it also requires:
1. An extremely capable sysadmin 2. A bunch of GPU capacity 3. That the timestamps be brute-forced separately
So it's not exactly a turn-key defeat of Akira.
if they don't release their code, then what's the point of having the code? they accomplished their task, and now here you go for someone else that might have the same need. otherwise, don't get infected by a new version