Spy anchor does not affect magnified box

[PhelypeOleinik]

The code:

\documentclass[tikz]{standalone}
\usetikzlibrary{spy}
\begin{document}
\begin{tikzpicture}[
    spy using outlines = {%
      magnification = 2,
      size = 3cm,
      connect spies,
      anchor = north, % <==
    }
  ]
  \coordinate (top) at (3,5);
  \draw (0,0) sin (top) cos (6,0);
  \spy on (top.north) in node at (3,2);
\end{tikzpicture}
\end{document}

produces:

where the spied on square doesn't match the magnified one. Notice that the in the top square the line touches the upper edge, but in the magnified square the line goes through the middle.

The code works correctly if I comment anchor = north. If I brute-force change the line:

pgf/tex/generic/pgf/frontendlayer/tikz/libraries/tikzlibraryspy.code.tex

Line 101 in 25d4a60

path picture={\node[anchor=center,tikz@lib@reset@gs]{\nullfont%

to read:

    path picture={\node[anchor=south,tikz@lib@reset@gs]{\nullfont%

instead, then the output is correct (only when anchor = north, of course).

I'm guessing that the anchor option in that node should account for the anchor of the upper node as well.