Obviously it should have been. When the track at Shawfield was being cut there was a manhole for a drain which would have been in the middle of the track on the entry to the first turn. It was reduced by about a foot lid replaced and covered over with shale, it never caused any problems with the track.
How could anyone scrape the shale to make that "groove" without being noticed? The ridge on either side of it is concrete that has been pushed out when the kerb was laid into the wet concrete.