I would never advocate for the strategy I proposed at a level where you would end up underwater (mortgage vs home value). At 40% equity, even a "big" home correction should be fine (although your ratio would obviously be much worse). Mentally, I don't like using a home as an ATM. Looked at from an investment perspective, most home owners are far too overweight in real estate. The baseline portfolios of xx percent equities and xx percent bonds didn't anticipate that your home equity could be far higher than your invested assets (in many cases 4:1 or more).A guy flogging his book on YouTube was pushing the concept of not paying off the mortgage and holding some liquid assets in case things crash and you need money to tide things over. If there is a price drop the bank may not be interested in adding to the loan. He referred to Evergrande and their situation because of a change in government policies.
I'm more like @Allistonfjr. My home is not part of my investment portfolio but I know a few people that have done very well by using their houses as investment vehicles.
Looked at another way, if you had a dwelling that kept you dry and safe, you can get that for xxx k dollars, the difference between that number and the actual value of your home is an investment in real estate that you get to enjoy. I've never seen any investment advice that pushed for more than half of your investible money to be in real estate.