Fair enough, though I think the problem space is substantially different (though I didn't mention it above). It's much easier to make (random) 3-SAT difficult

Fair enough, though I think the problem space is substantially different (though I didn't mention it above). It's much easier to make (random) 3-SAT difficult instances whereas for GI you needed highly structured graphs. Apparently Johnson graphs were one of the classes of graphs that caused people problems in GI.