The sharpness conjecture for upper bounds from circular plane integral point sets

Let $\overline{d}(2,n)$ denote the upper bound for the minimum diameter of a plane integral point set with $n$ points obtained from the circular constructions in Table

$$. **Sharpness conjecture.** The upper bounds from Table$$

are sharp.

The conjecture claims that the displayed constructions attain the corresponding optimal values, rather than merely providing upper bounds. The source does not provide a resolution of this claim.