Yes on 4th May both KM and GM signed the typewritten portuguese summaries of their respective individual interviews.
Can I ask you Pegasus. Is it clear that those were the summarised versions of the 'verbatim' statements which the police would use to type up their summaries? IIRC dates are not always shown on statements. (from memory)
IMO deciding what to put in and leave out of summaries (of interviews which took hours to complete) - would be a huge and obviously very important task and not something which could be done quickly. The verbatim statements would be extremely long and so I'm surprised if summaries were typed up and presented to the McCanns for signature on the same day as their interviews.
However, if that is what happened, then IMO it should not be forgotten that after having no sleep and long hours spent at the Police station, just hours after their daughter had disappeared, then they would be extremely tired and obviously full of anxiety.
There is a vast difference between having a statement read out to you by an interpreter- at their pace - and actually sitting down and reading a statement in English at your own pace - when any discrepancies would jump out of the page at you.
If they did sign statements which had mistakes in them on 4th May - then in the circumstances - I don't find that remotely surprising.