A small book could be written on the strangeness of the JSC. It would be fascinating to talk to those guys who made it and just ask them what was going on when they made it lol.

Now that I've been shown how to do it, I pretty much always manually IVTC because everything else fails too much. The JSC was too much for me but Darth Mallwalker IVTC'ed the whole trilogy for me. As long as there is only a cadence change once in awhile, manual ivtc is quite easy and reliable imo.

If the VBI was visible on the captured frames I'm pretty sure it could also be useful in avisynth. I'm sure a function could be written using averageluma() to automatically "read" the white flag line and determine if fields should be deleted or not, for example.