I understand that Calf_Cor is an extra bone that helps keep the knee shape when the leg is bent.
However, when the thigh is twisted and the leg’s facing direction turns, Cor does not fully follow the facing direction of the thigh and calf. So if I skin to Skin_*_Calf_Cor, the edge flow breaks.

Hello! Thank you as always for your interest in our tools.
We confirmed this as a double-knee twist bug, and we really appreciate you reporting it.
We will include the fix in the next build and release it.
For now, running the MaxScript below should resolve the issue.
(This assumes the default node names were not renamed.)
If anything else comes up, please contact us anytime!
-- MaxScript (assumes default node names were not renamed)
(
local sides = #("L", "R")
fn requireNode name = (
local n = getNodeByName name
if n == undefined do throw ("node missing: " + name)
n
)
fn applyCalf50Orient side = (
local dest = requireNode ("DrvPt_" + side + "_Calf_50")
local tgts = #(
requireNode ("DrvPt_" + side + "_Calf"),
requireNode ("DrvPt_" + side + "_ThighNoTwist")
)
local oc = Orientation_Constraint()
dest.rotation.controller = oc
oc.relative = false
local n = oc.getNumTargets()
for i = n to 1 by -1 do try (oc.deleteTarget i) catch ()
for t in tgts do oc.appendTarget t 50.0
try (oc.weight[1] = 50.0) catch ()
try (oc.weight[2] = 50.0) catch ()
format "ok % targets=% %\n" dest.name tgts[1].name tgts[2].name
)
undo "OrientConstraint Calf_50 L/R" on (
for side in sides do applyCalf50Orient side
)
)