Yes, but for some peripheral skills that might help but aren't really "necessary", this rule makes a lot of sense. I mean, spending 100 hours on a skill definit

Yes, but for some peripheral skills that might help but aren't really "necessary", this rule makes a lot of sense. I mean, spending 100 hours on a skill definitely wont make you an expert, but it'll make you literate in it. Taking the sales example, as a programmer it might teach you how to "sell" yourself to forge a better career. Or say public speaking.