You criticize PP for shallow analysis but your analysis of GRATs, GRUTs, and similar estate tax avoidance strategies is even more superficial and conclusory.
Again, if you are going to throw punches you ought to make really sure you’ve done your own homework.
As for the concrete, the important thing here is whether those repurchased shares retain their original cost basis or not (to the grantor) from the IRS's POV. If they do, all that's happened is a complicated tax-free cash transfer. If they don't, then cap gains taxes have been avoided.
So far as I understand the rules, it's the former. If I'm wrong, I'm happy to be pointed to a credible source etc.