Sorry to rain on the parade but, I've just had a very different experience with Public Beta 5. After installing PB4 on an external Firewire drive I found it would no longer boot. There was no option to switch to APFS. So, it was still HFS+.
Anyway, I booted to the 10.13 Recovery volume and re-installed macOS. It installed PB5 over the internet. During the process, there was no option to install APFS and the drive remained HFS+ – it was not automatically converted. So, I rebooted to the Recovery volume and opened Disk Utility to try to convert to APFS. Found the option greyed out. So, I currently have a running copy of PB5 which I can't convert to APFS.
I suspect that in the beta versions of 10.13, APFS is limited to Macs with an SSD. You've found that you got APFS automatically on a HDD. Perhaps that was because you also had an SSD. I don't know why that would be so but, anything goes with Apple's betas.
Apple have been playing very oddly with the implementation of APFS. In 10.12 I was easily able to convert the same Firewire drive to APFS. So, why not allow/provide for that in the 10.13 betas ?
I've stopped testing the PB as Finder bugs from 10.12.1 have still not be touched and I'm mainly interested in APFS.
Cheers.
Last edited by Beeston; 08/16/17 10:49 PM.
