On that specific point, quite a few threads on this. Effectively, you should think of award tickets, once bought, as just tickets on a given bucket which is very low down the pecking order of buckets.

So let's imagine that someone manages to book two of the cheapest revenue at a time inventory was Y9 B9 H9.... N9 V9 G9 Q9 04.

A couple of weeks later, their plans change and they change their tickets thereby releasing the two O bucket tickets that they purchased. However, by that time, the availability has drastically changed to Y9 B6 H0... N0 V0 G0 Q0 O0. The release of the two O tickets won't mean that suddenly two O tickets will reappear either on their own (… N0 V0 G0 Q0 O2 which is impossible) or coherently with other buckets (H2... N2 V2 G2 Q2 O2). What will happen instead is that maybe the availability will become Y9 B8 H0 or Y9 B8 H2 everything else 0. Exactly the same with award tickets. In particular, if you are down to V0 in economy or to R0 in business, the default outcome is definitely that your cancelling your award tickets will not lead to any award space becoming available.