why should she explain
I don't think there is the slightest reason for Kate to explain anything at all. She gave a list of the medication she had brought with her to the police in a statement. Which Amaral probably leaked to Felguieras making him the source of the calpol story much as he was the source of the majority of the myths put into the public domain.
Quite obviously 'Calpol' was yet another of the lies he fed to Sandra Feligueiras, as she has verified on Netflix.
SnipTranscript of TV Interview with Sandra FelgueirasHere is a transcript of Felgueiras' question and Gerry McCann's answer. Note that the McCanns at this point were still subject to Portuguese secrecy law and were restricted in what they were permitted to say on threat of legal sanction:-
Quote:
Sandra Felguiras: "In that evening, did you give to your kids something like Calpol to help them sleep?"
Gerry McCann: “You know we’re not going to comment on anything, but you know there is absolutely no way we used any sedative drugs or anything like that.”
http://madeleinemythsexposed.pbworks.com/w/page/39077700/Rebuttal%20of%20%22Fact%22%2013