Which police statement are you referring to? The one where he says he would not be unable to recognise the man again? Or the one where he isn't totally sure that the man was Gerry?
You seem to be a lot more certain that the Smiths saw Gerry than the Smiths were. Let's look at what Martin actually says:
In relation to the video clips of Gerard McCann and the person I saw on 3rd May 2007 when I saw the BBC news at 10 PM on 9th September 2007 something struck me that it
could have been the same person.
It was the way Gerard McCann turned his head down which was similar to what the individual did on 3rd May 2007 when we met him. It
may have been the way he was carrying the child either. I would be
60-80% sure that it was Gerard McCann that I met that night carrying a child.
I am basing that on his mannerism in the way he carried the child off the plane. After seeing the BBC news at 10 PM, footage on the 9th September 2007 I contacted Leicestershire police with this information. During that time
I spoke to all my family members who were with me on the night of 3rd May 2007 about this and
the only one who felt the same way as me was my wife.
IMO, what we are seeing here is along the lines of distinction bias. The Smiths admit they followed the case and for four months, they see Gerry in the news daily. Not once do they consider that this could be the person they saw. Then, just 2 days after the McCanns were made Arguidos, all of a sudden they are thinking "ooh, could Gerry have been the man we saw?" and their opinions and memories are influenced by this news that the parents are now in the frame. It's not a coincidence Martin Smith had this sudden epiphany as soon as the parents were declared suspects IMO.