Why not? What makes it different when it is passed from the terminal?

Why does interpolation happen only once? Because that is how it works

my $stuff = "\n newline gets interpolated at compile time";
my $other = "$stuff \n gets interpolated at run time";
@ARGV = qw( $stuff  $other NOINTERPOLATION );
print "$stuff\n$other\n@ARGV\n"
__END__

 newline gets interpolated at compile time

 newline gets interpolated at compile time
 gets interpolated at run time
$stuff $other NOINTERPOLATION
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See, $stuff and $other and @ARGV all get interpolated in that print call, but the values in @ARGV won't get magically interpolated once again