Even tax advantaged accounts are considered liquid, there is a penalty to liquidate them, but you have access to the funds if you need them and it is a formula that is easy to calculate. Account size minus taxes and if you are younger the 59 1/2 another 10% penalty.
When you apply for a mortgage, the bank considers your 401(k) and IRA as liquid assets, they pretty much bank (pun intended) on your willingness to liquidate those accounts rather than losing your house, it’s a psychological thing.
-Mister FancyPants