I've been testing out the 10.13 public betas as they come through. There has never been an option to convert to APFS. Early on I tried to convert using Disk Utility in the Recovery volume. That stopped the drive from booting and I had to do a clean install. In PB5, the option in Disk Utility to convert to APFS is greyed out.
Some online sources have noted that APFS does not work on HDD-only Macs. I have tested APFS on a non-boot drive under 10.12. It was great !
But is it likely 10.13 will not boot APFS on HDD-only Macs ?
Thanks.