It seems phrased in the particularly Apple-y style that usually means "we're seeing whether we're allowed to throw this legacy feature away or whether something will force us to put support for it back in."

More accurately: "we still need to see how badly this breaks Photoshop and iTunes or their builds."

Years ago, I used HFSX on my machine but I don't remember that iTunes broke because of that. A lot of other things broke though.

HFS+ can be configured to be both case-sensitive and not (the default). So in that sense it's a regression.

As I seem to remember running in case sensitive mode broke tons and tons of apps that made assumptions based on the history of HFS+ being case insensitive.

I'd be very interested to know if they run case-sensitive by default are not in the final release.