I think radial grids have been around for a long time. I recall a board done on the old Calay CAD that ran on the PDP11 that had to fit in the nose cone of an airplane that I think had parts laid out on a radial grid. The problem with radial grids was meshing them with the square grid.
In the old days grids were important. There was no automated spacing checking. The spacing was calculated by the grids you used. The boards would be laid out 8, 8 and 8 or 8 mil traces and 8 mil spaces on an 8 mil grid. By placing the 8 mil traces on the next grid that didn't contact the trace next to it, you would get the 8 mil spacing. If you laid out part of the board radially some of the pads wouldn't fall on the 8 mil grid and maintaining the spacing requirements would be difficult.
Today I switch grids while laying out a board all the time. The software maintains the spacing and checks for errors.
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