Not sure I agree there Woods. The granular make-up of the product had me wondering. I used it for the first time on slabs (Wednesday) on my own patio. Most of the joints were in the 10mm range. The perimeter joint was 35-40mm and around the chamber lids, slightly bigger.
I also had to do a bit of fettling and shaping at one of the slab edges and imagined that it would be tricky with the GeoFix, but it was actually a doddle. You can tool it and compress it also, although you do have to wait an hour or two.
Prior to my own patio I have been proper old school and always created mortar joints with (and joined to) the bedding mix. What sold it to me for the GeoFix was that we had to point a black cobbled (much driven over) rumble strip with it. Incredible gear.