Is it safe to assume that any prayer done for a very specific personal circumstance will likely have some parallel to prayers launched by others at some point in time, so that would allow some pooling, but for pooled prayers that are highly specific and don’t apply to many possible recipients, it will simply be skipped over?

This is the way it works. There are individual prayers not appropriate to pool with others, not just because there is no intention for allowing that, but it might be highly specific to their personal circumstances of the moment in a very narrow way that has only a limited applicability to others, particularly as one goes across time domains to many other eras with huge cultural differences and historical differences as well. This does not add any undue burden to the divine realm as we always survey the body of prayers available for deployment to see in what way can they be augmented or not, as the case might be. So this is simply widening the awareness that this is possible, and to have a human request at the time of generation will allow much more pooling than would otherwise happen, and represents a true benefit, not a liability in any sense.