In the canvas run, the same rows and cells stay in the page at opacity 0 over the canvas (ResultsTable.tsx on perf/53-canvas-grid), so each dragged frame may still be paying for style and layout on the ~1,500 new cells, with only their paint saved. Did you try a run with that layer cut down to the focused cell, to see whether the 66.7 ms dragged frames move at all?
csmlab notes
In the canvas run, the same rows and cells stay in the page at opacity 0 over the canvas (ResultsTable.tsx on perf/53-canvas-grid), so each dragged frame may still be paying for style and layout on the ~1,500 new cells, with only their paint saved. Did you try a run with that layer cut down to the focused cell, to see whether the 66.7 ms dragged frames move at all?