It used to be, but not anymore.
It has grown to be its own thing with some happenstance parenthood through being born from an early attempt at Perl 6, and thus is now only being slightly more related to Perl than e.g Ruby is. Ok I'm pushing it but you get the idea: taking a biological analogy, it has mutated away far enough that it is now considered to be its own strain.
And if that helps clear some doubts, Perl 7 is on the table (if there ever needs to be a Perl 7):
At some point in the future, the PSC may decide that the set of features, taken together, represent a big enough step forward to justify a new baseline for Perl. If that happens, then the version will be bumped to 7.0.
https://blogs.perl.org/users/psc/2022/05/what-happened-to-pe...So Raku cannot be Perl 6!