If Kiwifarms were just a proxy purchaser of the address space, I'd have expected it to be transferred to ARIN already. The actual purchasing company appears to have once existed: https://web.archive.org/web/20180224172917/http://flowchemical.com.au/ (e: though it doesn't seem to be a chemical company, I'd be surprised if Null was bored enough to put up a site for a shell company 7 years after the fact instead of taking the IP range and running). It seems to be defunct now, though.
I don't think that the eSafety Act allows the relief requested (confiscating the IP block). It's civil liability, not criminal liability. That being said, I'd fully expect APNIC to either completely ignore the issue (are they even covered by the eSafety Act? I'm not familiar with what a "designated internet service" is) or immediately fold.