R28 - CF Matching vs Multiple Liability Matching matching, everyone, invested

pawn

Since everyone has pretty much been discussing this reading, I have a question under this topic...

On pg. 46 of the text in the second paragraph it states that, "CF matching requires a relatively conservative rate of return assumption for short-term cash and cash balances may be occasionally substantial"

Is this because with CF matching funds are not fully invested and parked in short term yielding in investments (i.e money market securities or t-bills) for liquidity in order to meet a liability when due?

I'm confused by this?