Back pay UC - person awarded LCW & LCWRA

Hi Gordon and all
Wondered if you could advise? Person claims UC and is subsequently found to have LCW and LCWRA after a WC assessment. He is now getting the correct monthly amount. However, UC have told him, face to face at the job centre, and not over the phone, that his back pay which is owed is "being withheld - pending a case manager's decision whether or not he is entitled to any back pay" due to a change in the law in April of this year."

Am I right in thinking that this sounds wrong and they (UC) are confusing the extra amount given to people found to have LCW only since April of this year? But because he was found to have both LCW and LCWRA then the new ruling shouldn't affect him?

Any help would be very much appreciated.

Buster