um, options and treasuries settle the next day (not t+3 like stocks). also, if you have a margin account, money from the sale of stock is usually available that same day - i've withdrawn money the day of a sale, and wasn't even charged margin interest.
i've also found that this is not true from experience - while things like treasuries and agencies are highly liquid, there are many bonds, particularly "junk bonds" that have a slow (and sometimes non-existant) secondary market. in fact, fidelity tells you this fact on the trading screen when you try and purchase a fixed income security that is not considered "investment grade."
i still don't see why "retirement" money is not considered liquid - for example, i have some money sitting in a money market account in my roth ira; money that i contributed (not earnings). i could withdraw this money tomorrow without incurring any taxes or penalties. i don't see how this doesn't fit the standard of "liquidity."
lol, and by your books definition, houses are "illiquid" since they generally involve a long exhaustive search for a buyer