One of the requirements in JAR-FCL 1 (fixed-wing) for the issue of an ATPL certificate is valid CPL + IR certificates + valid ATPL theory.
One of the requirements in JAR-FCL 2 (helicopter) for the issue of an ATPL certificate is valid CPL(H) + IR(H) certificates. There is absolutely no requirement in JAR-FCL 2 that you need ATPL theory in any situation. ATPL (H) theory is still just a way of doing CPL + IR theory "at the same time".
I believe, which someone at the UK CAA confirmed, that they just copied the fixed-wing requirements in lasors and put it under the helicopter section as well. I few months ago I e-mailed the CAA about this but still no reply.
They might, however, change the theory requirements in the future but it is likely that "old" CPL + IR theory will still be valid for ATPL certificate issue.