I noticed in the article it was mentioned that the perceived change of direction of the constellation may have been due to a scribe error. I can imagine a not too interested or sleepy observer putting down the wrong data.
It’s good that you noticed that; the reason I chopped out a good bit (besides the 300 word limit — I used 296 up there) including her method of trying to fit it, is that it’s not the only time this is found in ancient records, and it ain’t about poor observing or lazy scribes, it’s found pretty much everywhere that records survive. And each time it is, those studying it try to make sense of it as if it represents the same conditions we have today.
I could see a scribe not doing his best work, especially since it was painted on the inside of a sarcophagus lid, viewed only by a dead man whose eyes were likely gouged out during the mummification process. He probably wasn’t too concerned about his critics ;)