Thanks for your investigations into this.
While I don't really like these sorts of loose ends and things I don't fully understand,
at the end of the day it's a very minor issue.
I can easily change the line endings with a short one-liner:
there's quite a swag of legacy code like this that I'll need to deal with in the not too distant future.
And, if I don't change them, the warning is harmless as far as I can tell:
there's no indications of side-effects or other problems waiting in the wings.
Perhaps bingos will have an answer; although, I don't think he visits very often.
I've encountered his name on many occasions in CPAN testers reports and the acknowledgements section of deltas;
however, checking his Writeups, his last post was over seven years ago in 2015.