The FCC doesn't work that way.When WBWC went for a power increase to go from 100 to 4,000 watts in the early 2000's there was no station at 88.3 FM in Painesville. However, either a license application had been filed, or might likely be filed, so the FCC carved out a space for it. The station at 88.3 FM in Painesville did not go on-the-air until 2008 or 2009, as I recall.
On the non-commercial end of the dial, there are no allocations the way there are on the commercial part of the dial.
Any application simply has to protect whatever stations are already on the air or have applications in the pipeline. The FCC doesn't "carve out space" anticipating future applications. It's entirely up to an applicant (and its technical consultant) to identify an open spot on the dial.
In this particular case, the application for what became WHWN was filed back in 1997 but was held up for a decade with FCC procedural issues, so it was already on the books and needed to be protected when WBWC went to increase power.