Pulling an all nighter every once in a while, or even a couple consecutive days during crunch time is not the same as working 20 hours per day. So unless you've got a specific quote from either of them I call bullshit.

That said, Bill Gates definitely said he and some of his crew were working 16 hour days delivering their first DOS release.

Point is, you might work some intense stretches, and doing that shows your passion and might land give you an edge when you need it. But you don't need to go insane. If you work 8 hours day job, don't spend hours in commute, you can be perfectly healthy spending 2 hours of your night time each day working a side gig.