/usr/lib/libstdc++.so.7 in Release 9.0 ?

[Makoto Fujiwara <makoto%ki.nu@localhost>]

Just a curiosity,
in the report
  http://mail-index.netbsd.org/pkgsrc-bulk/2021/01/31/msg020376.html
Some R-* are flagged, for example,

  math/R-minqa
  math/R-RcppEigen
  etc,

In their logs,  the string /usr/lib/libstdc++.so.7 appears,

------------
** testing if installed package can be loaded from temporary location
Error: package or namespace load failed for 'minqa' in dyn.load(file, DLLpath = DLLpath, ...):
 unable to load shared object '/work/math/R-minqa/work/.destdir/usr/pkg/lib/R/library/00LOCK-minqa/00new/minqa/libs/minqa.so':
  /usr/lib/libstdc++.so.7: version GLIBCXX_3.4.11 required by /work/math/R-minqa/work/.destdir/usr/pkg/lib/R/library/00LOCK-minqa/00new/minqa/libs/minqa.so not defined
Error: loading failed
Execution halted
ERROR: loading failed
------------

But if you look at the release binary (9.0):

/usr/lib/libstdc++.so.7 is not included 

sevan@makoto 00:22:06/210201(..binary/sets)% tar ztvf base.tar.xz|grep libstdc
lrwxr-xr-x  0 root   wheel        0 Feb 14  2020 ./usr/lib/libstdc++.so -> libstdc++.so.9.0
lrwxr-xr-x  0 root   wheel        0 Feb 14  2020 ./usr/lib/libstdc++.so.9 -> libstdc++.so.9.0
-r--r--r--  0 root   wheel  2030136 Feb 14  2020 ./usr/lib/libstdc++.so.9.0
lrwxr-xr-x  0 root   wheel        0 Feb 14  2020 ./usr/lib/i386/libstdc++.so -> libstdc++.so.9.0
lrwxr-xr-x  0 root   wheel        0 Feb 14  2020 ./usr/lib/i386/libstdc++.so.9 -> libstdc++.so.9.0
-r--r--r--  0 root   wheel  1968736 Feb 14  2020 ./usr/lib/i386/libstdc++.so.9.0

Why does libstdc++.so.7 appear in the log ?

Or am I looking something badly ?
Thanks,
-- 
Makoto Fujiwara
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