What you're talking about is a process that is used in some countries, not for whole blood donations, but for plasma donations. It's called “quarantine and retest”. A donor would give a plasma donation that is frozen immediately. We freeze that anyway as part of the normal production. It then sits in the freezer for four or six months. The donor then subsequently comes back and gives another donation. If the donor tests negative on that second donation, then you're allowed to release the one that's been in the freezer for four to six months. That's the one place in which one can hold blood products for release.
For the fresh components, it doesn't work, because platelets only live for five days and you don't have enough time to wait.