Another thing that doesn't match :
When you have this sort of sittuation, someone saying that CB killed MM it's normal for other Sta or even international police forces to call the Sta/BKA that makes the claim and check if there is any chance for the same suspect to be linked to the crime. Even on PK case it was "normal" for them to check with HCW/BKA if there was a link on the cases, because it's the NORMAL procedure.
Even with PJ, in the past they sent rogatory letters to other countries when other killers were found to check if the guys could be linked to MM. I did saw this in first hand on a case that I was working on the time.
What is NOT NORMAL is this :
Madeleine McCann Suspect Linked To Disappearance Of German Boy
It's not normal for the leader on the investigation on a case to call the parents of another missing child.
What what the intent of the call ? Just to tell Rene father that they were re-opening the investigation ? No way.
In other hand Rene was German and disapeared in Portugal so i guess it would be BKA to check this out but why call family of boy (that family were already conformed with a natural drowning) to say they were going to investigate CB on it ? It wouldn't be "natural" to investigate first and only then if they were sure that CB did the crime call the family ? Why to provide "false hope" ?
So we can assume that the phone call was not just to inform. Most likely they would like to know if family saw someone like CB near the place where CB went missing but then we have a problem again, first they contacted Rene father that was not on crime place (mother with boyfriend and Rene were) and 2) no public enquire neither mention on MM enquire for people to "remember" if they saw CB near the place RH went missing.
Many things going on that are "not normal" on investigations protocol.
Also what will HCW/BKA tell to René father if at the end they don't have anything to link CB to RH case ?
Something like - "Sorry to provide false hopes after those 20 years that you tought that your child did drown. You can think that again now because we can't blame CB after all".
If you were on the shoes of that family what would you think about BKA/HCW at the end ? Sorry but this is as bad as it gets ...