Strange 2 Cell Chains RC Ripples

In extremely difficult grids, 1 in 10 have an occurrence of an exclusive pair that allows a sub row/column eliminations. This is strange in that once the initial sub row/column eliminations are completed, it is rare to go back to that strategy after a more complex strategy has been applied. The sequence is as follows:

D4 & D6 have an exclusive pair, 69. Removal of other digits (78 from D4 & 28 from D6) leaves 8's in just one sub row, F 4-6.
8 can only occur in F4 & F6 so the 8's in F1 & F3 can be removed.

This particular cascade doesn't occur often but when it does, if missed, the grid is unsolvable.

MXQ

Introduction Initial Values Start Grid Sub RC Elimination 2-Cell Chains Strange 2C Chains Swordfish Patterns Re-Check/Refresh X-Wing Patterns 7C Swordfish 4-Cell Chains (Row) 4-Cell Chains (Col) Solution Change Tracking Re-Eng. Grids

Strange 2 Cell Chains RC Ripples