The dig did not show that Merlin was buried there.
Debated. The hillfort and the barrow are real finds. Merlin is not shown as a real person.
At Drumelzier, in Tweeddale in southern Scotland, Tinnis Fort stands over the place linked with Merlin's grave. The fort was in use in the late 6th and early 7th centuries AD. Across the River Tweed, a square barrow dates from the late 3rd century to the late 6th century AD. It held burials of people of high status. Older round barrows from the Bronze Age stand around it. A survey near the traditional spot found a shape in the ground like a grave. Pieces of flint blades, from the Late Mesolithic to the Early Neolithic, were found on the top of Tinnis.
The page says no one can confirm that the grave-shaped feature belongs to Merlin.
People told this story.
https://www.ancient-origins.net/news-history-archaeology/merlins-grave-drumelzier-0021373