It appears that this PR built on (was based on) https://github.com/ruby/ruby/pull/1747/files.

That seems perfectly reasonably to me in this case. Better than creating 2 completely independent PRs that both modified some of the same lines (requiring/forcing a conflict).

The only downside is that it arbitrarily chooses one PR to be the parent of the other, when they should more intuitively be thought of as siblings/co-equals.

I like how both PRs both say that they "This solves partially https://bugs.ruby-lang.org/issues/14097"