Indexes on 2 xattr fields is inconsistent

Create documents with any data.
Add two different system xattr fields to all documents ( _system1 and _system2 )

Try to query:
select meta().xattrs._system1, meta().xattrs._system2 from default where meta().xattrs._system1 is not missing and meta().xattrs._system2 is not missing

This will return an error:
"msg": "Plan error: Can only retrieve virtual xattr and user xattr or virtual xattr and system xattr"

Now create index on both xattr fields:
create index idx1 on default(meta().xattrs._system1, meta().xattrs._system2)

Now try to run previous query:
select meta().xattrs._system1, meta().xattrs._system2 from default where meta().xattrs._system1 is not missing and meta().xattrs._system2 is not missing

This will return no results instead of an error.

So either 1: index creation on two xattr fields should result in error or 2: I should receive results for the query with 2 xattr fields that uses the index.