There was a horrid smell reported in that car and the boot was left open!
The theory is simple: Keela detected Madeleine'a blood in the car boot. For that to happen in a car rented nearly a month after her disappearance the body was hidden on the beach then moved inside and stored in a freezer or her missing pink blanket with blood on was put in the boot re fibres and hairs found. Keela only alerts to human blood and the preliminary report said it matched (15 out of 19 alleles) Madeleine's profile and not any of the other family members.
Oh dear - Groundhog day again. It's clear to me PF that you either don't read or choose to ignore the explanations re the alerts in the boot both from the FSS and other posters who have explained it numerous times.
If there had been cadaverscent that strong present in the car then Eddie would have alerted to it. He did not. The material which Keela alerted to was so tiny FSS could not say what it was - only that it was 'cellular material. It is only the fact that Keela only alerted to blood that it is assumed that is what it was.
A statement by an anonymous person which is not in the files - and which IIRC Amaral claimed was handed to him after he was removed is not credible evidence IMO. (from memory so happy to be corrected if necessary)