The way it is written, it sounds like they are trying to hide the fact that said "legacy software" is part of the (new) system itself. Otherwise they wouldn't need to include it in the base install.

> Python, Ruby, and Perl

The order they use for the languages hides the fact that, at least for Catalina, Perl is by far the most used scripting language by core elements of macOS, even more than the shell. Check it by yourselves:

    file -b /{usr/,}{s,}bin/* |cut -d\  -f1,2|sort|uniq -c|sort -n|tail

     13 setuid Mach-O
     23 a /usr/sbin/dtrace
     50 a /usr/bin/perl5.28
     53 a /usr/bin/perl5.18
     81 POSIX shell
    116 Perl script
    954 Mach-O 64-bit