Did they have some ad-hoc temporary corpse storage? A small back-up pyramid?
God I hate when you go to check your sources and Reddit refreshes, deleting your comment -_-
So this happened a few of times during the Ramesside era. Typically the work on the tomb was rushed and shoddy because Egyptian religion mandated that a person be buried 70 days after death. A tomb that was meant to be large and luxurious might only end up having one or two completed rooms, and that at a lesser quality than intended. Sometimes plaster would be used instead of taking the time to carve into stone. Or sometimes a completed tomb may be taken over and the original owner’s name plastered over and carved with the new individual’s name. Sometimes these tombs were empty and hadn’t been used yet and may have belonged to a noble, or they’d straight up yeet a dead occupant and put them in a lesser tomb. The book The Lives of the Ancient Egyptians by Toby Wilkinson gives a great rundown on the lives of the workers at Medinet Habu, the village of workers who created the tombs in the Valley of the Kings. It’s a big book but not an overly difficult or academic read and I’m sure you can find it used if you’d like to learn more!