I saw this play when it happened, it was a foul, and it was a roller coaster ride. These are the stages of officiating grief experienced:
1) Didn't see a flag thrown - darn, they missed it

2) Announcers mention flag on field - all right, they got it!

3)

- uh oh, stay with it, stay with it!

4) Flag picked up -

I also wonder if the discussion was about where the block occured, but it was a good 3 yards beyond the LOS. A learning opportunity for all, and a reminder that it can happen to any of us, including the best in the business.
I'm sure clarification from said contributor would be instructive to all.