The Systematic Removal of Security in Consumer Operating Systems

On the HFS+ side, you should probably not be using HFS+ anymore. Not supporting encrypted file systems is one way to reduce the maintenance cost of keeping a file system before phasing it out definitely. It’s nice they do that in phases at least.

For more or less similar reasons you are not supposed to use ext2 or ReiserFS on Linux (you can, with enough determination), and I think both of these are much newer than HFS+.

> is support being dropped because the previous filesystem had strong encryption?

This statement seems to imply that APFS encryption is less secure than HFS+ encryption and no further evidence is given.