Earlier quoted context omitted.
The lower bound is generally very easy to measure precisely. So a change in that would be immediately noticed. For example, how long is the North Carolina coastline? No idea. But we can measure the precise distance between the point where that state's border with South Carolina meets the ocean, and the point where the border with Virginia meets the ocean. The coastline must be at least this long. And if you measure y…
Much more complcated problem than you're implying as NC has no unbroken coast. It's all shoals and barrier islands - and when you're inside that, swampland.
Unbroken coastline, shoals, barrier islands, etc, are all unrelated and irrelevant to the lower bound.
For example, the lower bound of the coastline of Canada is the straight-line distance from White Rock to Saint Andrew.