The route is vital.
If they debunk The Sea Wall it undermines the prosecution badly. They can't change routes mid trial. The other routes are also weaker & the defence would attack them.
But the defence knew The Sea Wall was unbreakable. So it was - 'it was possible but that doesn't mean he did'.
The words was " he used a route that avoided the back roads "
Wilkinsons statement was that the route was decent.
If the defence had countered it would have been up for deliberation who they believed.
Julie also said as Ainsley thought he would cycle the brook track not the sea wall.
So not massively detrimental the defence disputing the sea wall.