This is not something you can readily change. It is considered standard functionality. If you don't want these lots available run your UD program, (the one for skipped lots), more frequently, like every 5 minutes, and reduce the waiting time (in config), to 1 minute. These lots will be UD'd very quickly and won't be available for use then.

SAP leaves these available as in many places, they use skip lots in production. They produce an inspectiont lot for example on every ton of material made. But they only inspect every third ton. Should they get a failure, they can till use the skipped lots to test the two tons of material that were skipped, to determine exactly where the failure happened. If the lots had been processed, there would be no way to do that, it would have to be a very manual process. At the end of the day they run their skip lot UD program and if not issues had arisen, all the skip lots to the day would be posted and issued.