So what was the penalty?

The penalty was scoring a TD, based on the timing of the flag.

Said a WR was covered. He clearly wasn’t. Flag was thrown as the ball was headed to the end zone 40 yards behind the play and 5 seconds late.

What makes it so bizarre is the timing of the throwing of the flag for sure

That Williams was covered up and, therefore, not an eligible receiver.

He wasn’t covered up, clearly.

He wasn't covered up he was on the line of scrimmage and he didn't step out of bounds it was a completely phantom call.

Whatever they thought they saw was imaginary.

The only thing I think might have happened is the outside WR reported as on the line.

Only explanation that makes sense