The test itself may be the issue but other protected skills did work fine.  The clip was done with a Sorc loaded down with trash loot to slow animations.   You can clearly see the Sorc is hit in the middle of the iframe. 

The iframe has 2 phases: Phase 1 the crouch. Phase 2 the leap and move.  It appears the iframe works ok during the crouch in place phase but fails while moving in the iframe.  I could do the same test with other skills while loaded down with trash and NOT be knocked out of the protection.  e.g. I could float the Training Dummy and do a slowed down Crow Flare and the FG works just fine.

I submitted a detailed bug ticket.