The download page recommends 7-Zip to decompress the tar.gz on Windows. But the latest tarballs switched to PAX format, which 7-zip does not support, causing cut of filenames.
mediawiki-1.34.1.tar.gz: POSIX tar archive (GNU)\012- POSIX tar archive (GNU), file mediawiki-1.34.1/.phan/config.php, mode 0000664, uid 0001750, gid 0001750, size 00000012777, seconds 13637157252, user reedy, group reedy\012- data (gzip compressed data, was "mediawiki-1.34.1.tar", last modified: Thu Mar 26 17:13:38 2020, max compression\012- data)
mediawiki-1.34.2.tar.gz: POSIX tar archive\012- POSIX.1-2001 tar archive, extension ././@PaxHeader, mode 0000000, uid 0000000, gid 0000000, size 00000000033, seconds 00000000000\012- data (gzip compressed data, was "mediawiki-1.34.2.tar", last modified: Wed Jun 24 16:28:13 2020, max compression\012- data)
Workaround: extract using tar command from Git for Windows