In lieu of an official response here’s my interpretation.
There’s a commit that changes a hardcoded minimum speed of 0.05mm/s to a configurable minimum speed that can change by toolhead, the default for all 3 being 0.05mm/s
Minimum planner junction speed is documented as such
// Minimum planner junction speed. Sets the default minimum speed the planner plans for at the end
// of the buffer and all stops. This should not be much greater than zero and should only be changed
// if unwanted behavior is observed on a user's machine when running at very slow speeds.
Of course this would apply to all machines and I’m not sure why it was announced on a post talking about improvements to the AT and F models.