Apologies if this has been covered elsewhere in the thread.
I'm sure a couple of years ago home v Boro and Britt Assombalonga was about 5 yards offside when the ball was played forward, but the ref played on, he scored and the goal stood because Taylor Moore headed the ball back towards his own goal. I recall Sky saying that if TM hadn't played the ball it would have been offside, but his touch played BA onside (even though he was clearly off when the original ball was played forward).
What's the difference here?