theorem's target anchor is sometimes placed in the heading of the previous page if heading contains a \vbox

Test case (pdflatex):

\documentclass{article}
\usepackage{fancyhdr}
\pagestyle{fancy}
\usepackage{hyperref}
\newtheorem{thm}{Theorem}
\textheight60pt
\begin{document}
1\\2\\3\\4\\5\\6

\begin{thm}\label{th}
Theorem text.
\end{thm}
Ref to Theorem \ref{th}.
\end{document}

Checked with recent versions, each fails since 7.00w, 7.00v (and previous versions) are OK. (Perhaps since Feb 13, 2023 [new thm implementation]?)

Start by compiling the supplied minimal test case with pdflatex and compare the theorem anchor placement across the reported hyperref versions, especially 7.00w and 7.00v. Trace the new theorem implementation and hyperlink anchor handling to identify why the target moves to the previous page; done means the anchor is placed with the theorem on the correct page while the reference still resolves.