This reads to me like it is motivated by the all-too-common and deceptively flawed meme of "an array in scalar context gives its size while a list in scalar context returns its last element". I've seen that used to justify so very many flawed conclusions. You can also use it to make flawed justifications to quite a few "correct" conclusions, but that just demonstrates how the flaws in that meme are deceptive (which is probably part of why it is still "all too common").

The subroutine does /not/ return an array that then decides to give its size when it finds itself in a scalar context. There are many other ways that thinking "this sub returns an array" will mislead people. So it is better to divorce yourself from both of these flawed ways of thinking about context in Perl.

And, no, my objections are not based on some secret knowledge on how Perl works internally. They are based on repeatedly seeing people make mistakes about how Perl scripts would behave based on these ideas. There are lots of cases where these ideas give the right answer. But the cases where they lead to the wrong answers are surely more important.