The footnotes don't tell you the whole story. The truth is those verses were added, thereby corrupting the scripture.
Try John 7:53-8:11 or Mark 16:9-20. Same story.
“John 7:53-8:11”
The incident of the woman taken in adultery is in the oldest manuscripts, some after Luke 21:38 and some after John 7:36 and some after John 21:24. All that it proves is that the incident was factual but the scribes were ignorant of its exact position.