Testing with a metaoperator doesn't print the test description

I was writing tests on Complex arrays and I was using the Z≅ operator to check whether the arrays were approximately equal, when I noticed a missing test description.
I tried to golf the piece of code to find out the simplest case that shows the result I was seeing. The description is missing in the second test even when I use Num or Int variables and the Z== operator.

use Test;

my @a = 1e0, 3e0;
my @b = 1e0, 3e0;
ok @a[0] == @b[0], 'description1';     # prints: ok 1 - description1
ok @a[^2] Z== @b[^2], 'description2';  # prints: ok 2 -

done-testing;

Is there a simple explanation or is this a bug?