Here's my theory for reading before it gets whooshed.
Amaral never gave any credence to Jane Tanner's sighting, even less so when there were suspicions it was Murat.
I think he then saw Crecheman's statement & kept it in reserve as he pursued the McCanns. Once he had acquired enough "evidence" & they were charged, prosecution would have produced Crecheman so that the McCanns could not have used the unidentified Tannerman in defence of their claims of abduction. Whilst Smithman remained unidentified too, Tannerman could never be charged as Madeleine's abductor.
After the McCanns left Portugal & the PP didn't have enough evidence to charge them, cue M Smith to identify Smithman as Gerry. Take a fresh statement, move the time of the sighting on a bit then add that to all the other "evidence" which, in Amaral's eyes should have been enough. The presence of Crecheman could then have been revealed, Only it didn't work because Amaral was sidelined - so Crecheman's details remained buried & would have remained buried without the McCanns determination to get the investigation reopened.
IMO Crecheman was Amaral's Ace, which he never got to play - probably because he couldn't without incriminating himself after the UK authorities launched a review.
Amaral wants you to believe that Tannerman was Gerry & Smithman was Gerry - he said so in Chapter 20 of his book
Extract from Chapter 20 - An Irish Family In A State Of Shock.
"When we receive this information, at the end of September, we think we finally have the piece that will allow us to complete the puzzle. Because of this, we may be able to reconstruct the course of events on that cold night of May 3rd in Vila da Luz. We have a better understanding of why Jane Tanner, "sent," the alleged abductor in the opposite direction to that taken by the man seen by the Smith family. Suspicion had to be diverted from Gerald who - if he was the guilty party - would have taken this route: leaving apartment 5A, the individual who was carrying the child, did not go east, towards Murat's house, but west in the direction of the beach."
All my own opinion, exercising the same freedom of speech Amaral has been legally granted.