It is not really well defined how --pipe interacts with :::. The current behaviour is undefined.
Without running these, explain what you would expect these would do:
seq 23 | parallel -k --pipe -N2 cat\;echo {1}-{2} ::: a b c ::: A B C D E
seq 23 | parallel -k --xapply --pipe -N2 cat\;echo {1}-{2} ::: a b c
::: A B C D E
/Ole
