I did this repair...it started cracking almost immediately and gets worse daily. I may not have done it correctly, but I followed the steps and used all SEM products. It looked great when finished. Having said that, the cracks are hairline, but growing, but still MUCH better than the starting point which was as bad as the dash in the first pictures.
Worth doing and maybe you will have better results, but don't be surprised if your results are like mine.
In retrospect, I would put more of the flexible filler in and less of the foam. Like make a channel so the filler can be thicker. Reality is there is a lot of flexing that goes on with these cars. One crack started while we were installing the dash.
Picture below is after about 100 miles of driving.