"Lazy" I get, but when he says "dumb" I think "humble" conveys the idea better. You shouldn't be "too smart", but that's not the same thing as being dumb. Letting go of preconceived notions to get to the root of a problem may involve "playing dumb", but that's still not the same thing.
Still, "dumb" sounds less chest-beating than "humble" (ironically enough) so if you think you're not humble enough about being humble, by all means start calling yourself dumb instead. :-)
But "experienced" is another one of those glowing words (like "smart") that emphasizes you knew your way around in the past. This is an external marker, something other people judge you by and you can advertise with. When you have to solve actual problems, it's no good to think of yourself as smart and experienced, because that will only frustrate you if your amazing talents don't immediately suggest a solution. Taking yourself out of the equation and treating each problem by its own merits rather than your own merits is what's required, and that's the point of the "lazy" and "dumb" epithets: they're a deliberate kick to your ego, something programmers can usually use less of. Your talents can take care of themselves.
Still, "dumb" sounds less chest-beating than "humble" (ironically enough) so if you think you're not humble enough about being humble, by all means start calling yourself dumb instead. :-)