I don't understand any SWR below 3%.
You can get a 3% dividend yield, meaning you never touch the initial investment.
You can get a residential gross rental yield above 5% that will net above 3%. Again you will never have to touch capital. You can get higher rent yields on commercial property.
Any capital appreciation or depreciation is fairly irrelevant if the assets are owned for income, rather than growth.
If you shoot purely for capital growth you might fall short of 3% SWR due to a bad sequence of returns, but if you take a reasonable portion of income focussed assets, removing some risk of selling in a market slump, I think you can design something that will allow for 3.5% SWR+.
Well, 3% of dividends is not guaranteed. Efficient market hypothesis says that if it was, nobody would ever invest in bonds, since their yield is lower. Actually, I'm pretty sure s&p 500's yield is lower than that currently.
But anyway, I agree that anything below 3% is probably too conservative, especially since these studies are aiming people retiring at ages like 65, and hope to consume their portfolios in 30 years. I mean, come on, just keeping your stash from being eaten by inflation/fees/taxes is not that hard. I'm not talking about growing it, just fighting inflation et al. And, well, just that, just a 0% real return lets you eat 3.33% of your portfolio every year for 30 years. And what's the point in investing 50% in stocks if you can't even enjoy a bigger SWR than with, say, 100% TIPS?