Hey, interesting findings! I agree that the future features under the --preview flag continue to improve the black style. Black not splitting long string automatically surely is a bit tedious right now, though not really a deal breaker IMO :D

The description of the preview feater states

Experimental, potentially disruptive style changes are gathered under the --preview CLI flag. At the end of each year, these changes may be adopted into the default style, as described in The Black Code Style.

This sounds to me like functionality behind the --preview flag is more likely to be buggy, may change more frequently and may in the end not make it into the stable style. TBH [I do not think] the benefit of the gradually nicer style tweaks is worth this instability risk :/
A one-time change is ofc fine with me as long as the current black version accepts these changes :)