The page does not show that a witch was buried in the chamber.
Myth. The witch belongs to a later village story, not to the dig.
The chamber is at Leaval, above Loch Aisebhat, on South Uist in Scotland. Archaeologists say it is a Neolithic chambered cairn, about 6,000 years old. Four upright stone slabs form it, and the top stone is missing. Diggers found pieces of Neolithic pottery, flint tools, and quartz inside the chamber. They also found the line of a Bronze Age enclosure, and a round cut in the floor.
Archaeologists still do not agree whether that round cut was a posthole, part of the building work, or a pit left by later digging.
People told this story.
https://www.ancient-origins.net/news-history-archaeology/legend-meets-archaeology-00102999