What is sideline cash?

Mish quoted from Zero hedge:

Sideline Cash SillinessBarring trivial exceptions, sideline cash can never support asset prices for the simple reason for every buyer of equities there is a seller.
Money cannot flow into stocks or bonds. If $50 trillion in sideline cash purchased equities and bonds, there would still be $50 trillion in sideline cash.
The minor exception to the rule there is a seller for every buyer are new or secondary offerings, trivial in comparison to the alleged sideline cash theory.
Sideline cash is a function of Fed printing and the ability of banks to borrow money into existence.
Statement 1: Several weeks ago, my response was to say that all this money will support asset values going forward. That may have been too simplistic.WrongStatement 2: Just because there’s more cash in the financial system doesn’t necessarily mean that it’s available to buy securities, nor that it’ll prevent a repricing of debt and equities that have been propped up by years of unconventional monetary policies.Better, but still wrong, and missing a key point: In aggregate it cannot be used to buy securities.Sideline cash will keep rising as long as debt expansion and Fed printing continues, but not a penny of it can come into the markets, except for new or secondary offerings.There is no conundrum. Nor is there any such thing as “sideline cash”. Someone has to hold every penny printed into existence, at every point in time until reverse repos drain the cash.

Its not an issue of semantics.  What Mish is implying is that liquidity events ebentually result in a letter to Janet that balances assets and liabilities.   But, what really happened is tyhat the letter was wriyyen after some selected delay to obtain queue advantage.  Then the turn around ime means Janet is off in her estimate.  Ao, the sideline cfash isan approximation of whatm Mish says, and he is the one who invented the Fed uncertinty princfiple:

assets=liabilities to some precision defined by the Fed Uncertainty.  If the Fed is uncertain to 4%, the assetts equal liabilities as a six bit integer only.  That is what your invention means, Mish,  you cracked the case.