It's not all that strange to think that time preference is culturally informed. That's the Weber thesis. It's also not all that strange to think of it as genetically determined - low time preference is a fantastic trait to evolve if you want to set up your ancestors for success (granted, first you have to evolve an ability to think abstractly about time in the first place).
All of this meshes very well with Keynes's assertion that savings behavior is as much about psychology as it is a response to economic incentives.
I would also highlight that although Khan only mentions time preference as it relates to savings - it will also relate to investment and the sorts of investments we make. A lot of very important public investments: space colonization, basic research, addressing climate change, etc. are hampered by a high discount rate and short time horizons.
Bryan Caplan also has a post on savings, specifically addressing the critique that expansionary monetary policy and tax cuts won't work because "people will save it". He accepts the liquidity preference justification for the increased savings, and then essentially says "well what's so wrong about satisfying that preference"? I have three thoughts:
1. He does raise a good point that eventually consumer demand could be augmented by satisfying consumer's liquidity preference, but
2. The real glitch isn't consumption - it's investment demand. Now, maybe once corporate liquidity preference is satisfied, they'll start investing because they feel safer. But they're not going to start investing in response to lower interest rates - that's the essential point of the liquidity trap. When cash and bonds become interchangeable because interest rates are so low, further expansion is not going to stimulate activity through lowering the interest rate. Could it stimulate activity through satiation of liquidity preference? Perhaps. But,
3. Wouldn't it be a whole lot quicker, and wouldn't it avoid the risk of substantial inflation after the recovery, if we just augmented demand with fiscal policy? This might not be as attractive if we didn't have a bunch of potential public investments, but... ummm... we do have a bunch of public investments.
I've been fairly agnostic about the monetary policy route - I don't think it holds a ton of promise right now, but I haven't put a lot of effort into shooting it down either. Caplan presents a plausible case for how it could work, but it just seems like it would take so damned long.