True, that's another good point. But again, this reasoning is very different to the one from the linked article and website - if you have oprofile or valgrind's cachegrind available, you clearly could get perf setup instead.

I'm not debating that manual GDB sampling has its place and value. I'm debating that perf is "lying" or that it's impossible to get hold of off-CPU samples, or profiling of multithreaded code in general.