Yes, ($a, $b, $c) is a list in that, syntactically, there are some scalars and they are separated by commas. But I don't think that's the interesting sense of 'list' in the context of Perl. In:
$x = ($a, $b, $c)
, ($a, $b, $c) do not constitute a list because they are never on the stack together. That's why that code assigns $c to $x, whereas:
$x = @a = ($a, $b, $c)
assigns 3 to $x. It is just as easy for someone to get into trouble by not
understanding what is meant by a Perl list.
In the documentation, the word 'list' certainly appears in places where it does not mean "a grouping of scalars on the stack". I don't think it follows from that, however, that there cannot be a specific meaning for 'list' as shorthand for 'Perl list'.