Issue with capt-of package

This warning comes from the caption package, not capt-of. See section 6.5 of the caption documentation for details of hypcap.

Quoting from pp. 37--38 of the documentation of the caption (!) package:

\captionof{htypei}{. . . } vs. \captionsetup{type=htypei}+\caption{. . .}

Without hyperref loaded, both will give you identical results. But with hyperref loaded, and with hypcap=true requested, the hyperlink anchor will be placed different. For example:

\begin{minipage}{\linewidth}
. . .
\captionof{figure}{A figure}
\end{minipage}

will place the hyperlink anchor at the caption. (And if hypcap=true is set, you will get a warning about this.)